PERTH, Australia (AP) - An Australian aircraft Thursday detected what may be the fifth signal coming from a man-made device deep in the Indian Ocean, adding to hopes that searchers will soon pinpoint the object's location and send down a robotic vehicle to confirm if it is a black box from the missing Malaysian jet.
The Australian air force P-3 Orion, which has been dropping sonar buoys into the water near where four earlier sounds were heard, picked up a "possible signal" that may be from a man-made source, said Angus Houston, who is coordinating the search off Australia's west coast.
"The acoustic data will require further analysis overnight," Houston said in a statement.
If confirmed, the signal would further narrow the hunt for Malaysia Airlines Flight 370, which vanished on March 8 while flying from Kuala Lumpur to Beijing with 239 people aboard.
The Australian ship Ocean Shield picked up two underwater sounds on Tuesday, and two sounds it detected Saturday were determined to be consistent with the pings emitted from a plane's flight recorders, or "black boxes."
The Australian air force has been dropping sonar buoys to maximize the sound-detectors operating in a search zone that is now the size of the city of Los Angeles.
Royal Australian Navy Commodore Peter Leavy said each buoy is dangling a hydrophone listening device about 1,000 feet below the surface. Each buoy transmits its data via radio back to the plane.
The underwater search zone is currently a 500-square-mile patch of the ocean floor, and narrowing the area as much as possible is crucial before an unmanned submarine can be sent to create a sonar map of a potential debris field on the seabed.
The Bluefin 21 sub takes six times longer to cover the same area as the pinger locator being towed by the Ocean Shield, and would take six weeks to two months to canvass the current underwater search zone. That's why the acoustic equipment is still being used to get a more precise location, U.S. Navy Capt. Mark Matthews said.
The search for floating debris on the ocean surface was narrowed Thursday to its smallest size yet - 22,300 square miles or about one-quarter the size it was a few days ago.