Underwater signals that focused the search for missing MH370 are no longer believed to have come from the black box, according to a 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 box, 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.
"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.
If the pings had come from the recorders, searchers would have found them, he 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," Dean said.
Other countries involved in the search had reached the same conclusion, he told CNN.
Australia is leading the search for the plane which vanished on March 8 en route from Kuala Lumpur to Beijing with 239 people onboard and is using the Bluefin-21 mini-sub until new equipment can be obtained.