Angus Houston, the retired Australian air chief marshall in charge of the Flight MH370 search based in Perth, says new signals are believed to be those of a flight recorder.
He says it could take some days to confirm the two signals, which have been detected at a depth of 4500m by the Australian Navy ship Ocean Shield.
"We want more confirmation before we say this is it," he says.
The first signal was held for two hours 20 minutes until it was lost. It was then detected agains for a much shorter period.
While Flight MH370 flew for an estimated 7.5 hours, the voice recorder only captures the last two hours. However, the flight data recorder has the last 25 hours of cockpit conversation.
The reported depth is at the limits of capability for underwater vehicles. Air Chief Marshall Houston also says there’s a need to fix the location of the signal before sending an underwater vehicle.
British navy ship HMS Echo is towing a pinger locator in an area of the Southern Indian Ocean where Australian and Chinese vessels have both picked up acoustic "pings" that could be from the flight recorder of missing Malaysia Airlines flight MH370.
Australian authorities responded to reports that a Chinese patrol ship Haixun 01 had detected ultrasonic “pings” matching the frequency put out by the beacon on a flight recorder.
The recorders, also known as "black boxes" although they are actually orange, have a limited battery life that is expected to expire in this case any time soon, nearl;y a month after the Malaysian Airlines Boeing 777-300 went missing on March 8.
The Australian search leader, retired air chief marshal Angus Houston, says underwater detection gear towed behind an Australian navy ship, the Ocean Shield, has also detected a sound.
Up to 12 aircraft and 13 ships were sent out yesterday, focused on three large stretches of ocean about 2000km from Perth.
News of the Haixun 01’s discovery first emerged late on Saturday night via the Chinese state media agency Xinhua, which has a reporter on board, but was treated with caution by search authorities until a further signal was picked up by the Ocean Shield.
The Haixun 01 ping had a frequency of 37.5kHz – the same as that emitted by flight recorders – and was detected at about 25 degrees south and 101 degrees east, within the 216,000sq km search zone. The Xinhua report said the signal was heard for about 90 seconds.
Mr Houston says another “fleeting” signal was picked up 24 hours earlier by the Haixun 01, on Friday afternoon. The two detections took place about 2km apart.
“In an ocean that size two kilometres is not a large distance,” he says, adding the lead was “encouraging [but] unverified until such time as we can provide unequivocal determination.”
The third signal was detected on Sunday morning by the Australian navy ship Ocean Shield, located around 300 nautical miles away from the Chinese ship. It was not immediately known whether it was one the same 37.5kHz frequency.