India, April 26 -- The mystery surrounding the death of Matthew James Sullivan, who had been circulating claims about UFOs, has taken a decisive turn after authorities confirmed his cause of death as an accidental drug overdose, per the New York Post.

This comes as officials begin an investigation into a "possible sinister connection" as the number of dead or missing space specialists reaches 14.

The New York Post reported that Rep. Eric Burlison (R-Mo.) expressed "grave concern" about the unexplained death and sent the case to the FBI for examination because of "implications for national security."

In a letter, Burlison sent to FBI Director Kash Patel, he wrote, "Mr Sullivan's death was a local Virginia medical examiner case, and the ...