开始水下搜寻马航失踪客机黑匣子

Crews in the remote southern Indian Ocean have begun the underwater hunt for the missing Malaysian jetliner's flight data recorder, which is set to run out of battery power in just a few days.

Retired Australian Air Chief Marshal Angus Houston said Friday a U.S. Navy towed pinger locator is being dragged across a 240-kilometer track to try to detect a signal from the black box.

Authorities estimate they have only until around Monday before the batteries run out on the black box's locator beacon, which transmits electronic signals, or pings.

That date marks 30 days since the Boeing 777 mysteriously vanished en route from Kuala Lumpur to Beijing. A massive, multinational search effort has turned up no traces of the jet.

On Friday, an expanded team of 14 airplanes and nine ships continued their so far fruitless mission of looking for possible signs of wreckage floating on the ocean surface.

Houston, who is heading up the Australian agency coordinating the search, said crews have not given up hope of finding some debris floating on the water.