A nuclear physicist and MIT professor fatally shot outside his Massachusetts residence. A retired Air Force general missing from his New Mexico home. An aerospace engineer who disappeared during a hike in Los Angeles.

These are among at least 10 individuals connected to sensitive US nuclear and aerospace research who have died or disappeared in recent years, prompting concerns whether they are connected and fueling speculation online about the possibility of nefarious activity.

The FBI now says it “is spearheading the effort to look for connections into the missing and deceased scientists,” adding that it “is working with the Department of Energy, Department of War, and with our state … and local law enforcement partners to find answers.”

Separately, the Republican-led House Oversight Committee announced Monday it will investigate reports of the deaths and disappearances of the individuals, whom it said had access to sensitive scientific information.

The reports “raise questions about a possible sinister connection” between the deaths and disappearances, the committee said in its statement, seeking briefings on the matter from the FBI, the Defense Department, the Department of Energy and NASA.

The Defense Department said only that it would respond to the committee directly, and the Department of Energy referred questions to the White House.

In a post on X, NASA said it is “coordinating and cooperating with the relevant agencies” in relation to the scientists.

“At this time, nothing related to NASA indicates a national security threat,” NASA spokesperson Bethany Stevens said.

The cases vary widely in circumstance. Some involve unsolved homicides, while others are missing persons cases with no signs of foul play. In at least two instances, families have pointed to preexisting medical conditions or personal struggles as explanations. Authorities have not established any links between the cases.

The White House said last week it is also working with federal agencies to probe any potential links between the deaths and disappearances, with President Donald Trump referring to the matter as “pretty serious stuff.”

“It’s very unlikely that this is a coincidence,” House Oversight Chair James Comer, a Republican, told “Fox News Sunday.” “Congress is very concerned about this. Our committee is making this one of our priorities now because we view this as a national security threat.”

Rep. James Walkinshaw, a Democrat who also serves on the Oversight Committee, agrees an investigation into the disappearances and deaths is warranted, but he said he is not convinced there is a coordinated motive behind the cases.

“The United States has thousands of nuclear scientists and nuclear experts,” Walkinshaw told CNN’s Erin Burnett on Tuesday. “It’s not the kind of nuclear program that potentially a foreign adversary could significantly impact by targeting 10 individuals.”

The string of mysterious deaths and disappearances began in 2023, lawmakers say, with the death of Michael David Hicks, a scientist who worked at NASA’s Jet Propulsion Laboratory for nearly 25 years.

Hicks, 59, died July 30, 2023. During his career at JPL, he specialized in comets and asteroids, according to the American Astronomical Society. His cause of death was not disclosed.

His daughter, Julia Hicks, told CNN her father had been struggling with known medical issues and that the recent speculation has her “shaken up.”

“From what I know of my dad, there’s no train of logic to follow that would implicate him in this potential federal investigation,” she said. “I don’t understand the connection between my dad’s death and the other missing scientists.”

“I can’t help but laugh about it, but at the same time, it’s getting serious,” Hicks said.

Hicks told CNN no one in elected office or at any federal agency had reached out to her to inquire about her father’s death as of Tuesday afternoon.

In the years since, several others connected to JPL have also died or disappeared: Frank Maiwald, a specialist in space research, died in Los Angeles in 2024 at 61. Monica Reza, a 60-year-old aerospace engineer, disappeared while hiking in a Los Angeles forest in June 2025. She served as the director of the NASA Lab’s Materials Processing Group, the House Oversight Committee said.

Also missing is William Neil McCasland, a retired Air Force major general, who hasn’t been seen since he walked out of his Albuquerque, New Mexico, home on February 27, leaving behind his phone, prescription glasses and wearable devices. The FBI is now involved in the search.

McCasland was at the center of some of the Pentagon’s most advanced aerospace research and once commanded the Air Force Research Laboratory at Wright-Patterson Air Force Base. Months after the 68-year-old went missing, officials still can’t say where he went, why he left or whether someone else was involved.

His wife, Susan McCasland Wilkerson, disputed at the time speculation that his disappearance was tied to his work at the base — long rumored to house extraterrestrial debris linked to the alleged “Roswell incident,” despite Air Force denials.

“It is true that Neil had a brief association with the UFO community,” McCasland Wilkerson said in a Facebook post. “This connection is not a reason for someone to abduct Neil. Neil does not have any special knowledge about the ET bodies and debris from the Roswell crash stored at Wright-Patt.”

“No sightings of a mothership hovering above the Sandia Mountains have been reported,” she added.

McCasland Wilkerson did not respond this week to CNN’s request for comment on this story.

Two others missing, Melissa Casias and Anthony Chavez, worked at the Los Alamos National Laboratory, a leading nuclear research facility in New Mexico.

Casias, 53, was last seen walking on a highway near Talpa, New Mexico, in June 2025, according to New Mexico State Police, leaving her belongings at home and a phone that had been factory-reset, NBC News reported.

The New Mexico Department of Public Safety told CNN there is an open missing person investigation into Casias’ disappearance but added no foul play is suspected.

Chavez, a 78-year-old retiree who worked as a foreman supervising construction at the site, also disappeared in May 2025, according to Los Alamos police. A detective told CNN there are no signs of foul play, but exhaustive searches have yielded no signs of activity or indications he was planning to leave.

His friend Carl Buckland told CNN he’s glad authorities are looking into the case: “It’s about time.”

In recent months, the deaths of several acclaimed scientists have also fueled speculation.

A professor at the Massachusetts Institute of Technology, Nuno F.G. Loureiro, was fatally shot at his home near Boston in December 2025 by a gunman who also opened fire on Brown University’s campus, killing two students. The 47-year-old physicist and fusion scientist had led MIT’s Plasma Science and Fusion Center, where he aimed to advance clean energy technology and other research.

Carl Grillmair was fatally shot at the age of 67 at his home outside Los Angeles in February. Authorities arrested a suspect who they don’t believe knew Grillmair, according to KABC. The astrophysicist worked at the California Institute of Technology, collaborated with NASA and was renowned for his studies on the search for water on planets outside our solar system.

Former US Air Force intelligence officer Matthew James Sullivan, 39, also died in 2024 before he could testify in a federal whistleblower case about UFOs, Rep. Eric Burlison of Missouri said, urging the FBI to investigate. His public obituary did not state how he died. CNN has reached out to his family.

Burlison, however, told Fox News that Sullivan died by suicide, calling it suspicious.

“He was scheduled to come in for an interview. Within two weeks, he had suspiciously committed suicide,” Burlison, a Republican, told Fox News.

In recent days, the 2022 death of Amy Eskridge has gained attention. Eskridge, 34, co-founded the Institute for Exotic Science in Huntsville, Alabama, according to her obituary.

Eskridge’s family said in a statement to CNN she was a “marvelously intelligent person” and suffered from “chronic pain.”

“People should realize that scientists die also and not make too much of this,” the family said.

Trump said he hopes the disappearances and deaths are just a coincidence.

“I hope it is random, but we are going to know in the next week and a half,” Trump told reporters Thursday, adding he had a recent meeting on the subject.

The White House declined to elaborate on the meeting.

The White House is “actively working with all relevant agencies and the FBI to holistically review all of the cases together and identify any potential commonalities that may exist,” White House press secretary Karoline Leavitt said in a statement on X on Friday.

The investigation is being carried out “in light of the recent and legitimate questions” regarding the recent cases and “no stone will be unturned,” she said.

“We’re going to look for connections … on whether there are connections to classified access, access to classified information, and or foreign actors,” FBI Director Kash Patel told Fox News on Sunday. “If there’s any connections that lead to nefarious conduct or conspiracy, this FBI will make the appropriate arrest.”

Correction: An earlier headline on this story mischaracterized the professional background of at least one of the individuals described. The headline has been updated.

CNN’s Jason Morris, Annie Grayer and Kit Maher contributed to this report.