At least 10 people linked to sensitive research have died suddenly or disappeared, prompting speculation and conspiracy theories

The FBI and a congressional committee are investigating the mysterious cases of 10 missing or dead scientists and staff who worked at sensitive nuclear or space technology laboratories.

Social media has “lit up” with theories about the disappearances and deaths, said CBS News, as speculation has “swirled” about whether they are part of an effort to “harm” US nuclear or space programmes.

William Neil McCasland, a retired US air force general now director of technology at an aerospace defence firm, went missing from his home in Albuquerque, New Mexico, on 27 February.

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Investigators soon became aware of other aerospace and nuclear officials and researchers who have gone missing or died in mysterious circumstances. These cases included a nuclear physicist and MIT professor who was fatally shot outside his Massachusetts home, an aerospace engineer who went missing during a hike in Los Angeles, and two scientists working on nuclear fusion and astrophysics who were murdered in their homes.

“The similar circumstances of some of the disappearances” and the subjects’ involvement in sensitive and secret research have “fuelled speculation about whether coordinated foul play or foreign espionage may be involved”, said The Hill.

The FBI confirmed it is “spearheading the effort to look for connections” between the 10 cases that have come to light and the Republican-led House Oversight Committee said it will examine “questions about a possible sinister connection”. In a post on X, Nasa said that it was cooperating with the investigations, but “at this time, nothing related to Nasa indicates a national security threat”.

The speculation has drawn in the US president. “I hope it’s random, but we’re going to know in the next week and a half,” Donald Trump told reporters, confirming that an investigation was under way. It is “pretty serious stuff” but “hopefully a coincidence, or whatever you want to call it”.

People familiar with the cases said that what “underlies” these deaths and disappearances is “not a spy-thriller plot”, but “something more personal and tragic”, said CBS News.

McCasland’s wife said in a Facebook post that it “seems quite unlikely that he was taken to extract very dated secrets”, pointing out that her husband retired from the air force more than 12 years ago.

The cases are “scattered across several years at different and only loosely affiliated organisations”, said Joseph Rodgers, from the Center for Strategic and International Studies. “If all of the scientists were working on one project or weapons system, then I’d be more suspicious,” he said.

A former US Department of Energy official was more succinct. “People do just die,” they said.

  Chas Newkey-Burden has been part of The Week Digital team for more than a decade and a journalist for 25 years, starting out on the irreverent football weekly 90 Minutes, before moving to lifestyle magazines Loaded and Attitude. He was a columnist for The Big Issue and landed a world exclusive with David Beckham that became the weekly magazine’s bestselling issue. He now writes regularly for The Guardian, The Telegraph, The Independent, Metro, FourFourTwo and the i new site. He is also the author of a number of non-fiction books.