PERTH, Australia - Search crews hunting for the missing Malaysia Airlines jet have failed to relocate faint sounds heard deep below the Indian Ocean that officials said were consistent with a plane's black boxes, the head of the search operation said Tuesday.
Angus Houston, the retired Australian air chief marshal who is heading the search operation far off Australia's west coast, said sound locating equipment on board the Ocean Shield has picked up no trace of the signals since they were first heard late Saturday and early Sunday.
Time is running out to find the devices, whose locator beacons have a battery life of about a month. Tuesday marks exactly one month since the plane vanished.
"There have been no further contacts with any transmission and we need to continue that for several days right up to the point at which there's absolutely no doubt that the batteries will have expired," Houston said.
Houston said the Ocean Shield crew may spend several more days towing sophisticated U.S. Navy listening equipment deep within the ocean to try and find the sounds again. Only at that point, Houston said, would a sub on board the ship be sent below the surface to try and chart out any debris on the sea floor. If it maps out a debris field, the crew will replace the sonar system with a camera unit to photograph any wreckage.
Houston's comments contradicted an earlier statement from Australia's acting prime minister, Warren Truss, who said search crews would be starting the Bluefin 21 autonomous sub on Tuesday.
The towed pinger locator detected late Saturday and early Sunday two distinct, long-lasting sounds underwater that are consistent with the pings from an aircraft's "black boxes" -- the flight data and cockpit voice recorders.
Houston dubbed the find a promising lead in the monthlong hunt for clues to the plane's fate, but warned it could take days to determine whether the sounds were connected to Flight 370, which vanished March 8 on a flight from Kuala Lumpur, Malaysia, to Beijing.