A nuclear generator filled with plutonium disappeared atop the Himalayas during a secret, failed CIA mission that is yet to be fully disclosed.
The device was taken to the mountains by a team of American and Indian mountaineers to spy on China, a recent New York Times report revealed. After it was lost, the governments of both countries tried covering it up as fears of environmental safety and radiation risks created panic.
The incident took place in October 1965.
The mountaineers' mission was to carry a monitoring device, which would be powered by a portable nuclear generator, to the top of the Nanda Devi, a highly dangerous and inaccessible peak in the range standing at 25,645 feet.
The portable nuclear generator was powered by roughly a third of the total amount of plutonium used for the bomb dropped in Nagasaki. Apart from the Pu-239 isotope, which was used in the atomic bomb, it also contained Pu-238, a highly radioactive fuel. The device weighed around 57 kilograms and was designed to withstand the freezing temperatures.
The team was sent out by the CIA investigate after the US suspected that China was developing nuclear weapons.
The purpose of the device was to spy on the neighbour and intercept radio signals from the country’s missile launches and tests.
In September, they set off to the second-highest mountain in India, even as expert climbers thought the mission was a gamble. They went under the guise that they were on a scientific research mission.
The highest-ranking Indian military captain on the team, M.S. Kohli, recalled the incident to TNYT, saying, “I told them it would be, if not impossible, extremely difficult."
In October, as the team neared the summit, a severe snowstorm struck
In an effort to save the team’s lives, Kohli ordered the mission to be abandoned immediately. “Secure the equipment. Don't bring it down,” he told the team over the walkie-talkie.
The visibility on the mountain dropped, and there was no food or water.
The device was tied to an ice ledge at Camp Four, and the climbers left the mountain for safety.
When they returned, the nuclear-powered device was missing, never to be seen again. The mission had failed in its final stage.
The device is believed to have been buried under the snow and glaciers.
A recovery team was sent out in 1966; however, the entire ice ledge was found to have been swept away, possibly by an avlanche.
American climber Jim McCarthy said that the warmth from the device could have caused the surrounding ice to melt, making it sink into the glacier.
In the 1970’s a scandal had broken out. Despite tense relations between the two countries, US President Jimmy Carter and Indian Prime Minister Moraraji Desai worked together in secret to bury the incident.
There is still worry that the highly toxic plutonium left in the mountains could melt and contaminate the Ganges River. Maccarty said that he later developed testicular cancer due to exposure to radiation on the mission.
After a landslide near the Nanda Devi killed 200 people in 2021, the speculations about the nuclear device resurfaced. Many locals doubt that the heat from the missing generator could have played a role.
Kohli died in 2025 at the age of 93. Many of the climbers, close to the end of their lives, lived in fear ever since the incident.
The lost nuclear device is still a concern for locals, according to the report, as glaciers in the mountains are rapidly melting due to climate change, and the frequency of floods and landslides keeps increasing in the area.
While experts say that they worry the plutonium could fall into the wrong hands and could be used to make nuclear weapons.
The incident is a reminder of Cold War paranoia and the geopolitical unaccountability of governments.