SYDNEY - Acoustic transmissions at the heart of the search for missing Malaysia Airlines Flight 370 are no longer believed to have come from the plane's black box, a US Navy official said Thursday.
The Navy's deputy director of ocean engineering Michael Dean told CNN there was now broad international agreement that they came from some other man-made source unrelated to the jet that disappeared on March 8, carrying 239 people.
But the Navy took issue with Dean's comments, which threaten to plunge the marathon and costly search into new confusion and extend the agony of relatives who are desperate for closure.
Dean said if the ping-emitting beacons, detected in early April in the southern Indian Ocean, were from the on-board data or voice recorders they would have been found by now.
"Our best theory at this point is that (the pings were) likely some sound produced by the ship... or within the electronics of the towed pinger locator," Dean said.
"Always your fear any time you put electronic equipment in the water is that if any water gets in and grounds or shorts something out, that you could start producing sound." He said it was not possible to absolutely exclude that the pings came from the black boxes, but there was no evidence now to suggest they did.
A US Navy spokesman retorted: "Mike Dean's comments today were speculative and premature, as we continue to work with our partners to more thoroughly understand the data acquired by the towed pinger locator.
"As such, we would defer to the Australians, as the lead in the search effort, to make additional information known at the appropriate time." The Australian-led Joint Agency Coordination Centre (JACC) made no immediate comment.
The US Navy pinger locator, dragged by the Australian ship Ocean Shield, was used by searchers to listen for underwater signals in the remote southern Indian Ocean in an area where satellite data indicated the plane went down.
A series of signals it picked up prompted Australian Prime Minister Tony Abbott to say he was "very confident" they were from the black box of the plane that vanished en route to Beijing from Kuala Lumpur.
It led to the deployment of a US mini-sub to scour the sea bed, but despite an extensive air, surface and underwater search, no sign of the jet has been found.