The House Benghazi committee has interviewed two drone sensor operators who were working on the night of the deadly 2012 attacks in Libya, including one who identified himself on talk radio as "John from Iowa."

The unidentified drone operator has earned derision from the Pentagon and committee Democrats, who say the GOP-led panel has made a series of costly, duplicative and unnecessary requests — including some based on claims made on Facebook or talk radio.

The drone operator, an Air Force sergeant on active duty, told a radio host in 2013 he was surprised that no one from Congress had contacted him.

Rep. Trey Gowdy, R-S.C., chairman of the Benghazi panel, said Thursday that "talking to enlisted service members with firsthand information is just as important as talking to the generals and admirals who command them. I appreciate the important work of these airmen, their service to our country, and their willingness to talk to our committee."

Gowdy has said he expects to issue a final report "before summer" on the September 2012 Benghazi attacks, which killed four Americans, including U.S. Ambassador Chris Stevens. Questions about security at the U.S. diplomatic facility have dogged Democratic presidential candidate Hillary Clinton, who was secretary of state at the time.

A senior Pentagon official, Stephen C. Hedger, criticized the Republican-led investigation in April, saying the panel has made a "crescendo" of costly, duplicative and unnecessary requests, including some based on claims made on Facebook or talk radio.

Hedger, an assistant secretary of defense, expressed frustration with the Benghazi panel's potentially futile calls for witnesses and information, including some that were later withdrawn. Hedger also challenged a line of questioning of current and former military officials that focused on hypotheticals suggested by committee members or staff.

Gowdy and other Republicans defend the inquiry and say the Obama administration has repeatedly thwarted their efforts.

"As it turns out, John (from Iowa) was exactly who he had claimed to be and still on active duty with the Air Force," the Benghazi committee said in a statement Thursday.

While Hedger and other Pentagon officials claimed the Defense Department was expending "significant resources to locate" the drone operator, "the Air Force knew exactly who had called into the talk radio show in 2013," the committee said.

Details of the closed-door interview with the two drone operators were not released. The interviews come a day after the panel interviewed retired Army Gen. Carter Ham, the former commander of U.S. Africa Command.

Spokesman Jamal Ware said the committee will continue interviewing witnesses as long as necessary, but said Gowdy is "still pushing" to meet a self-imposed deadline to issue a report before summer.