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Two More Signals Picked Up In Plane Hunt
A navy ship has picked up two further signals from what could be the black boxes of missing flight MH370.
Search coordinator Angus Houston described the "reacquiring" of sounds two more times by search teams as "encouraging".
It brings the total number of times the signal has been detected by the Australian naval vessel Ocean Shield to four.
ADV Ocean Shield first detected the sounds late on Saturday and early Sunday before losing them.
Mr Houston said the ship relocated the signals on Tuesday afternoon and then later that night.
An analysis of the earlier signals found they were stable, distinct and clear sounds that had a consistent pulse, indicating they were from a plane's black box.
"They (the analysts) believe the signals to be consistent with the specification and description of a flight data recorder," he said.
"It's nothing natural. It comes from a man-made device."
The new signals may allow the search to be concentrated on a much smaller area of the southern Indian Ocean, and open the way for the use of an unmanned submarine to look for wreckage.
Mr Houston said: "I'm now optimistic that we will find the aircraft, or what is left of the aircraft, in the not too distant future - but we haven't found it yet, because this is a very challenging business."
Earlier, it was feared the audio signal from the plane's black boxes may have died.
And Mr Houston acknowledged time was running out, noting the signals picked up on Tuesday were weaker and briefer than those heard over the weekend.
"So we need to, as we say in Australia, 'make hay while the sun shines'," said Mr Houston.
China's Haixun 01 vessel initially reported some acoustic signals south of where the Ocean Shield sounds were detected.
But Mr Houston said the signals heard by the Chinese ship have not occurred again.
The data recorders could provide critical information about what happened to the aircraft, which disappeared on March 8 with 239 people on board.
It is thought the airliner crashed into the Indian Ocean after veering thousands of miles off course.
Authorities say evidence indicates the plane was deliberately diverted by someone, but have not ruled out mechanical problems.