(Xinhua) -- Fifty years on, Du Xueyou still hears the deafening sound of China's first nuclear bomb in a remote northwestern desert on Oct 16, 1964. He was there. He helped create it.

GO TO THE FRONT

The story begins with the film "Gold-Silver Sands," or "Jinyintan" in Chinese. The film depicted the lives of herdsmen living on the grasslands of the same name in a Tibetan autonomous prefecture in northwest China's Qinghai Province. It became a hit when it was released in 1954.

Despite obvious critical and market success, it was withdrawn from theaters soon after a short public appearance, with no specific reasons given.

Du didn't get to see the film, but a mysterious trip four years later would connect him to its disappearance from cinemas.

Early in the winter of 1958, Du, 23, then a hoist technician with a mining machinery factory in Luoyang in central China's Henan Province, left his pregnant wife for a mission unknown. He was on a train heading west with several dozens of his colleagues. None of them knew what the exact destination was.

"All I knew was to go to the front," Du told Xinhua.

After almost a whole day on the train, they were transferred to trucks, which carried them to a barren grassland over another two days. The place, which is known by locals as Jinyintan, covers an area of more than 1,100 sq km and features plains surrounded by mountains on the Qinghai-Tibet plateau.

In the summer of that year, Jinyintan was selected as the location of China's first nuclear testing base, a Chinese counterpart to Oak Ridge, the U.S. "Atomic City" established in 1942.

Du was told they would build a factory there, and he knew its name later -- Factory 221. But again, he didn't know what the factory would produce.

"We were told not to pry, but we guessed it must be something big, and it had something to do with national defense because '221' is more like a military code name. We were all excited," Du recalled.

However, the "big project" had to start from zero. Du recalled he spent the first night on Jinyintan in a self-made tent and it was snowing all night.

"We put on all the clothes we had, but found we all became Santa Clauses the next morning as our faces were all frosty," Du said.

That's all it took to disillusion him.

The hardship was far beyond his imagination. The height of construction from 1959 to 1961 coincided with a nationwide famine caused by natural disasters. Du found himself in survival mode as the food supply quota per person was only 10 kg per month.

"We were so starving that our legs were swollen, a typical sign of malnutrition. We had to look for mushrooms and hunt in the mountains for food," recalled Du.

Despite the hardships, the base was built in 1963. Du took his first bath in five years that summer. He was given an even bigger bonus -- a vacation back to Henan to visit his family, including his five-year-old son he had never seen in person.

While Du was back for a long-awaited family reunion, Liu Zhaoming, an explosives engineer, left a Beijing-based institute for an unknown destination.

"I was only told to go to the front," Liu told Xinhua.

He also arrived at Factory 221 and worked in an explosives lab.

"You could never imagine how simple the lab's facilities were. We used bronze saws to cut the explosives with no insulation protection at all. It was really dangerous. After all, an explosion could happen any time," said Liu.

Liu had no idea that he was one of more than 10,000 scientists and engineers working for the country's first atomic bomb. They worked in more than 400 factories and scientific research organizations, which were scattered among 20 provincial regions. They were preparing different parts of the bomb and most of them didn't know the final product was a nuclear weapon.

On 6 June 1963, China successfully detonated a quasi-atomic bomb, which contained no nuclear material, at the Jinyintan base, paving the way for its first formal nuclear test.

NORTH BY NORTHWEST

Du was once again on a train westward to a "mysterious front" at the end of 1963. The destination was Lop Nur in the desert of the Xinjiang Uygur Autonomous Region, more than 1,600 km northwest of Jinyintan.

He and his colleagues worked on the construction of a new nuclear test base. It seemed overwhelming to start. However, a 102 meter-tall tower to carry China's first atomic bomb was raised in the Gobi within several months.

"People often ask me how you can keep on working under such extreme difficult conditions. I tell them I didn't know the feeling of not being hungry before I was 15, when the New China (People's Republic of China) was founded in 1949 and changed my life," he said.

"Most of my colleagues had gone through the same dark days as I did. So, we were clear about what people's lives were like when their home country was weak and bullied. I believed if I worked hard enough, my child would not have to live a childhood of suffering as I did," said Du.

"That's why the bomb was later called the bomb of courage," he said.

A declassified official record said that a total of 5,058 people, including Du, participated in the final preparation for the bomb's detonation in Lop Nur.

The last group of workers evacuated from the bomb site to an observation spot 60 km away after the detonators were connected to the atomic bomb at 6:30 a.m. on Oct. 16, 1964.

"I was one of the last group of people leaving the site. I didn't know the bomb actually exploded before my eyes. I didn't think of the dangers at all, just feeling time going too slowly," said Du.

At around 3.p.m., a concussive detonation rumbled through the desert, and Du saw a mushroom cloud rising from the Gobi. On that day, China successfully conducted its first nuclear test, making it the fifth nuclear-armed state after the United States, the Soviet Union, Britain and France.

"I was so happy that I took off the goggles and my hat, cheering with the crowd. A solider nearby reminded me to put on protection. I owe him a lot. Without him, my eyes would have been damaged," said Du.

The night after the explosion, the Chinese government published a declaration, announcing that the bomb was made for defense use and to break the "nuclear monopoly." It also promised that "at no time and under no circumstances will China be the first to use nuclear weapons."

Liu Zhaoming heard the news through radio that night, and one month later, he saw the mushroom cloud of the nuclear test in a documentary only shown at Factory 211.

"Finally, I could confirm that my work over the past 18 months had actually been for making an atomic bomb," said Liu.

"I felt proud and relieved. The 'Cold War' tension was high at that time. Those who opposed atomic bombs must have the bomb first. It was an inevitable choice for China to develop its own nuclear weapons at that time," he said.

UNDYING RELICS

Later at the Jinyintan base, China successfully developed its first hydrogen bomb and conducted nuclear tests 16 times.

The Chinese government suspended its nuclear weapons program on July 30, 1996. Prior to that, it gradually converted the once secret nuclear testing bases and sites into civilian areas.

The Jinyintan Base was abandoned in 1987. It was handed over to the Qinghai Provincial Government in 1993 when tests showed that environmental factors in the locality met international standards.

Many places in the region had no names, just code numbers. The former atomic city was given the name Xihai Town, the regional capital of the Haibei Tibetan Autonomous Prefecture.

Du and Liu, both retired from Factory 221, moved to live in a special compound built in downtown Xining, the provincial capital of Qinghai, for some 600 former atomic city workers in 1990.

"I sort of put the bomb behind me, but I can never forget it. For me, it was the most profound experience of our lives," Du said.

Many of his former colleagues and neighbors have passed away over the past 24 years. Now, only about 300 remain alive. Their stories are known to few people, even to their own families.

Tao Wenzhao, a professor of international politics and relations at Beijing-based Renmin University of China, called for public awareness of the secretive past.

"To remember the past is to commit oneself to the future. The spirit of sacrifice, cooperation and perseverance of the older generation is a treasure for all time," said Tao.

"Though the world is no longer in the restless fears of nuclear war or threats since the Cold War ended in the 1990s, nuclear weapons remain a symbol of power for big countries. They will still be there and the whole world needs to work together for peace," he said.

Jinyintan underwent a similar journey of alienation and re-engagement. An atomic energy museum, built on the former military zone, opened to the public in 2009. It has since become a major tourist attraction.

Du returned to Jinyintan in 2010 for the first time in two decades as a visitor to the museum. All his memories were reawakened. After a long silence, he said, "I hope I will never hear the same sound again."

(Reuters) - The United States has not seen any definitive indication of a transfer of power in North Korea, where state media have not mentioned leader Kim Jong Un's activities in weeks, a top U.S. official said in an interview broadcast on Sunday.

Kim's absence from the public eye has fueled speculation over the state of his health and whether he may have been sidelined in a power struggle.

"Obviously we are watching very carefully what's happening in North Korea," national security adviser Susan Rice said in an interview broadcast on NBC's "Meet the Press". "We have not seen any indications of a transfer of power at this point in North Korea that we view as definitive but we'll continue to watch it carefully."

North Korea's state media, which usually report Kim's activities in detail, have not mentioned any public appearances since he attended a concert on Sept. 3. The official KCNA news agency indicated he did not attend an important political anniversary on Friday.

Kim is still in firm control of his government but hurt his leg taking part in a military drill, a source with access to the secretive nation's leadership told Reuters last week.

It was not clear why a leg injury would keep him out of sight for so long, although it was not the first time he has been missing from view. Six months after coming to power, state media failed to report on or photograph him for 23 days.

Speculation on his health was stoked by a North Korean television report late last month that he was suffering from discomfort.

On Friday his name was not on a list of those who visited a mausoleum to mark the ruling party's anniversary.

Mr Kim has not been seen for more than a month, the longest hiatus since he came to power in 2011.

State television last month said he had an "uncomfortable physical condition" and later showed him limping.

On Friday, South Korea said it believed Mr Kim remained in control of the communist state.

"It seems that Kim Jong-un's rule is in normal operation," Unification Ministry spokesman Lim Byeong-cheol was quoted by Yonhap news agency as saying.

"With regard to his specific health conditions, our government has no information to confirm yet," he said.

Health problems?
On Friday North Korean officials visited Kumsusan Palace, a mausoleum for late leaders Kim Il-sung and Kim Jong-il, to mark the 69th anniversary of the Workers' Party.

For the first time in three years, Mr Kim's name was not included in the list.

The young leader, who inherited power after his father Kim Jong-il died in 2011, has not been seen in public since 3 September.

His absence has led to speculation over both his health and his grip on power.

(AP) — Toxic gases and ash from still-erupting Mount Ontake forced Japanese rescue workers to call off the search for more victims Monday as dozens of relatives awaited news of their family members.

Rescuers found five more bodies near the summit of the volcano, bringing the death toll to 36. They have managed to airlift only 12 bodies off the mountain since the start of the eruption on Saturday because of dangerous conditions.

How the victims died remains unclear, though experts say it was probably from suffocating ash, falling rocks, toxic gases or some combination of them. Some of the bodies had severe contusions.

Survivors told Japanese media that they were pelted by rocks from the eruption. One man said he fled with others to the basement of a lodge, fearing that the rocks would penetrate the roof.

Yuji Tsuno, a veteran mountain photographer, was near the summit. After taking pictures of the initial explosion as ash and debris rained down, he quickly took refuge in a nearby hut, he told the TBS TV network.

About 20 minutes later, when the smoke partially subsided, he rushed out and began his descent. It was a gamble, but he believed it was his only chance, he said.

"I almost thought it was the end of my life," he said in the interview.

On his way down, he spotted a man heading up. "I told him to go down with me, but he said he had to check on his child up there. I couldn't stop him," Tsuno said.

The eruption caught seismologists by surprise. Although somewhat increased seismic activity had been recorded for about two weeks, there were no indications of a major eruption, said Satoshi Deguchi, a Japan Meteorological Agency official in Nagano prefecture. Typical signs, such as increased seismic rattling or underground structural movement, were not detected.

Japanese TV showed soldiers carrying a series of body bags on Monday morning to a military helicopter that had landed in a relatively wide-open area of the now bleak landscape, its rotors still spinning.

The bodies were flown to a nearby athletic field and then taken to a small wooden elementary school in the nearby town of Kiso, where they were being examined in the gymnasium.

Family members of the missing waited at a nearby municipal hall.

More than 200 soldiers and firefighters, including units with gas detection equipment, were part of the search mission near the peak, said Katsunori Morimoto, an official in the village of Otaki.

The effort was halted because of an increase in toxic gas and ash as the volcano continued to spew fumes, he said, adding that the rescuers reported a strong smell of sulfur.

The eruption was the first fatal one in modern times at the 3,067-meter (10,062-foot) mountain, a popular climbing destination 210 kilometers (130 miles) west of Tokyo. An eruption occurred in 1979, but no one died.

The mountain began erupting at perhaps the worst possible time, with at least 250 people taking advantage of a beautiful fall Saturday to go for a hike. The blast spewed large white plumes of gas and ash high into the sky, blotted out the midday sun and blanketed the surrounding area in ash.

Hundreds were initially trapped on the slopes, though most made their way down by Saturday night.

About 40 people who were stranded overnight came down on Sunday. Many were injured, and some had to be rescued by helicopters or carried down on stretchers.

Japan's Fire and Disaster Management Agency said 59 people had been injured, including 27 seriously. It was trying to determine if any people were still missing.