Three more U.S. senators received a classified Pentagon briefing on Wednesday about a series of reported encounters by the Navy with unidentified aircraft, according to congressional and government officials — part of a growing number of requests from members of key oversight committees.

One of them was Sen. Mark Warner (D-Va.), the vice chairman of the Senate Intelligence Committee, whose office confirmed the briefing to POLITICO.

“If naval pilots are running into unexplained interference in the air, that’s a safety concern Senator Warner believes we need to get to the bottom of,” his spokesperson, Rachel Cohen, said in a statement.