“There are no details; it is literally an object,” Ms. Martin added. “It is based on satellite imagery. There is a plane en route to the area.”

It was not immediately clear why her agency said there was only one object when Mr. Abbott said there were two.

Cmdr. William J. Marks, the spokesman for the United States Navy Seventh Fleet, which has helped oversee the American military contribution to the search for the missing plane, said in a brief email on Thursday that he had not heard word of finding any objects possibly from the aircraft.

On Wednesday, Commander Marks said, “If suspect debris were spotted, the aircraft would more than likely use the EO/IR camera at close range to identify exactly what was detected.” He was referring to a camera with electro-optical and infrared functions that can discern objects much more sharply than a naked human eye. The aircraft, he added, “could provide the necessary information to lead salvage ships to the wreckage.”

Image Flight Lt. Russell Adams of the Royal Australian Air Force piloting his plane over the southern Indian Ocean during the search for Malaysia Airlines Flight 370. Credit... Sgt. Hamish Paterson/Australian Government Department of Defense, via European Pressphoto Agency

As the possible break in what had been a fruitless search was being pursued, the Malaysian authorities were seeking help from the F.B.I. to help retrieve deleted computer data from a homemade flight simulator belonging to the captain of the Malaysia Airlines jet that vanished 11 days ago, their first request for high-level American assistance in solving the mystery of the missing plane.