In an extraordinary development the underwater signals that focused the global search for missing MH370 are no longer believed to have come from the black boxes, according to a senior US Navy official.
The Bluefin-21, operating from the Australian navy’s Ocean Shield vessel, has been searching a remote area of the Indian Ocean where four acoustic transmissions, believed to have come from the aircraft's black boxes, were detected in early April.
The US Navy's deputy director of ocean engineering Michael Dean told CNN there was now broad agreement that they came from some other man-made source unrelated to the jet that disappeared on March 8 carrying 239 people.
However the US Navy has put out a statement saying that "it has been working cooperatively with our Malaysian, Australian and international partners for more than 2 months in an effort to locate MH370."
"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 "premature" revelation came Wednesday as searchers wrapped up the first phase of efforts, having scanned 329 square miles of southern Indian Ocean floor without finding any wreckage from the Boeing 777.
Mr Dean told CNN that if the pings had come from the recorders, searchers would have found them.
According to CNN Mr Dean said "yes" when asked if other countries involved in the search had reached the same conclusions.
"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," Mr 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."
However he told CNN that it is not possible to absolutely exclude that the pings came from the black boxes, but there is no evidence now to suggest they did.
Search officials had expressed "cautious optimism" in the pings when they were discovered on April 5 and 8.
This stemmed from the fact that they were located where Inmarsat satellite data indicated was the last communicated with the aircraft and the fact that the transmission rate of one ping a second was consistent with the black box signal.
However there was concerned at the time that the frequency was not quite right and that they were detected some kilometers apart.
Officials have told AirlineRatings.com that if the Inmarsat data is wrong they have “no idea” where the Boeing 777 is.
Mr Dean confirmed to CNN that the Bluefin-21 was not able to look at one area in the northernmost ping area because of the depth of the water there.
Australia is now negotiating with private underwater search companies to conduct the next phase, which will resume after the first phase of ocean mapping in two months, if not longer.
Total search area is 60,000 square kilometers.
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