CANBERRA, Australia (AP) — A U.S. Navy spokesman on Thursday dismissed as “speculative and premature” an American expert’s reported comments that the acoustic “pings” at the center of the search for the missing Malaysian plane did not come from the jet’s black boxes.

CNN reported that the Navy’s civilian deputy director of ocean engineering, Michael Dean, said most countries now agreed that the sounds detected by the Navy’s Towed Pinger Locator in April in the southern Indian Ocean came from a man-made source unrelated to the jet, which vanished March 8 with 239 people on board.