In what represents a new theory over the Malaysia Airlines plane that disappeared Friday with 239 people on board, investigators now say they think the plane may have “disintegrated” in mid air.

Investigators in Malaysia say that the lack of debris from the disappeared Kuala Lumpur to Beijing flight could indicate it “disintegrated” in mid air, according to an update by Reuters.

“The fact that we are unable to find any debris so far appears to indicate that the aircraft is likely to have disintegrated at around 35,000 feet,” a source, who is involved in the investigations in Malaysia, told Reuters.

Asked about the possibility of an explosion, such as a bomb, the source said there was no evidence yet of foul play and that the aircraft could have broken up due to mechanical issues.

But David Learmount, operations and safety editor for Flight International, said he would be very surprised if the authorities knew for sure that the plane “disintegrated” in mid air, Britain’s Sunday Telegraph reported.

It said Learmount added that it was not unusual to fail to find debris immediately after a crash, pointing out that it took time to find the evidence and uncover the facts.

“We just have to accept that, for the moment, we do not know what has happened,” he said.

“It’s also worth remembering that it took two days for any wreckage from the Air France crash in June 2009 to be found – and two years for the full operation to be completed.”

Telegraph also reported that in a further development – initially deemed to be significant – Vietnamese authorities said a military plane had spotted at sea an object suspected to be part of the missing airliner. But less than an hour after the statement was made, Vietnam said the objects had turned out to be nothing to do with the plane.

The crew of the DHC-6 plane saw the debris, some 60 miles south-south west of Tho Chu islands, but could not see any marks or identifiable signs.

Datuk Azharuddin Abdul Rahman, director general of Malaysia’s department of civil aviation, said that the debris was not from the plane.

“In the meantime, we are still verifying if the oil slick it matches the MAS Boeing 777-200 with relevant authorities,” he said.

He added that the search radius has also been expanded from 20 nautical miles to 50 nautical miles.

“At present, we have 34 aircraft and 40 ships currently combing the search and rescue areas,” he said.

•Photo courtesy London Evening Standard shows a little girl weeping over the fate of the missing plane and its passengers and crew.