Rep. Tim Burchett, a Republican from Tennessee, is warning about a series of incidents involving American scientists and researchers who have either gone missing or been killed over the past year, saying the pattern deserves closer attention. He also claims intelligence agencies have blocked his efforts to obtain more information about the cases.

Burchett pointed to multiple individuals in advanced scientific fields whose circumstances remain unclear. Among them is William Neil McCasland, a 68-year-old retired Air Force general and former commander of the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio. McCasland, who oversaw billions of dollars in research programs, was reported missing in New Mexico on Feb. 27. He was also known to have associations with unidentified flying object research circles.

Another case involves Monica Reza, a 60-year-old rocket scientist with ties to McCasland, who disappeared in June while hiking in California’s Angeles National Forest. Reza was credited with developing a rocket-engine alloy in work connected to NASA.

Burchett also referenced the December killing of Nuno Loureiro, director of the Massachusetts Institute of Technology’s Plasma Science and Fusion Center, who was shot at his home in Brookline, Massachusetts. In a separate case, California Institute of Technology astrophysicist Carl Grillmair, 67, was shot and killed on his porch last month after a long career studying planetary systems and astronomy.

In comments to the Daily Mail, Burchett suggested the number of incidents appears unusually high within certain scientific sectors and raised concerns about secrecy surrounding sensitive research areas, including unidentified aerial phenomena. He said the federal government has not been forthcoming with information and called for greater attention to the issue.

Authorities have not publicly linked the cases, and details surrounding several of the incidents remain under investigation.