FBI investigates mysterious deaths and disappearances of scientists working on nuclear and space research. Chris Swecker, a former assistant director for the FBI, discusses what he considers the 'common denominator' in the cases and more.

House Republicans are pressing multiple federal agencies for answers about reports that at least 10 individuals tied to sensitive U.S. nuclear and aerospace programs have died or disappeared in recent years, with lawmakers pointing to public reporting that raises questions about a possible "sinister connection" between the cases.

In letters sent Monday, House Oversight Committee Chairman James Comer, R-Ky., and Subcommittee Chairman Eric Burlison, R-Mo., request briefings from the FBI, Department of Energy, NASA and Department of War, citing what they describe as "unconfirmed public reporting" surrounding the incidents.

The lawmakers say the reports involve individuals with connections to "U.S. nuclear secrets or rocket technology" who have "died or mysteriously vanished," and are seeking to determine whether any broader national security risk exists.

"If the reports are accurate, these deaths and disappearances may represent a grave threat to U.S. national security and to U.S. personnel with access to scientific secrets," Comer and Burlison wrote.

House Oversight Committee Chairman James Comer, R-Ky., pictured here, and Subcommittee Chairman Eric Burlison, R-Mo., requested briefings from the FBI, Department of Energy, NASA and Department of War.  (Tom Williams/CQ-Roll Call, Inc)

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In response to earlier outreach, the War Department said there are "no active national security investigations" involving any current or former personnel tied to the reported cases.

The White House has acknowledged the issue but has not confirmed any connection between the incidents. 

Press secretary Karoline Leavitt recently said officials are working with relevant agencies to gather more information, while President Donald Trump told reporters he had "just left a meeting" on the matter, calling it "pretty serious stuff" and indicating answers could come soon.

The letters cite several individuals whose deaths or disappearances have drawn public attention, including former NASA Jet Propulsion Laboratory scientist Michael David Hicks, who died in 2023.

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Among the more recent cases, retired Air Force Maj. Gen. William "Neil" McCasland disappeared from his Albuquerque, New Mexico, home in February. Authorities said he left behind personal items but took his wallet and a firearm, and he has not been located.

NASA materials engineer Monica Reza, who served as director of the Materials Processing Group at the Jet Propulsion Laboratory, also remains missing after disappearing during a hike in California in June 2025.

NASA materials engineer Monica Reza, who served as director of the Materials Processing Group at the Jet Propulsion Laboratory, also remains missing after disappearing during a hike in California in June 2025. (Los Angeles County Sheriff's Department)

Jason Thomas, left, Melissa Casias, center, and Frank Maiwald are among scientists whose deaths or disappearances have drawn scrutiny as officials review whether any cases are connected. (Fox News: Sierra Casias: Legacy.com)

The cases cited in public reporting span a range of circumstances, including disappearances, confirmed homicides and deaths where no foul play has been identified. Authorities have not indicated that the incidents are linked.

Lawmakers also referenced reports suggesting a possible professional connection between some of the individuals through past Air Force–funded research programs involving advanced materials for space and weapons systems, though no confirmed link between the cases has been established.

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Comer and Burlison said the situation warrants further review, requesting staff-level briefings from the agencies by April 27 on any information they have regarding the individuals, as well as the procedures in place to protect sensitive scientific personnel and classified research.

The inquiry spans agencies responsible for nuclear weapons infrastructure, advanced military research, federal law enforcement and space exploration — a wide-ranging effort to determine whether any risk to U.S. national security or personnel connected to advanced research programs exists.

Fox News Digital has reached out to the departments that received letters for comment. 

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