A pinger locator has detected signals consistent with those emitted by aircraft black boxes, raising hopes of finding the missing Malaysia Airlines plane a month after it mysteriously disappeared en route to China.

An Australian vessel searching for the Boeing flight MH370 has detected signals consistent with those from aircraft black boxes, Air Chief Marshal (retd.) Angus Houston, the head of the Joint Agency Coordination Centre (JACC) which is leading the search, said on Monday.

Calling it the “most promising lead” so far, Mr. Houston said that Australian defence vessel Ocean Shield acquired the signal twice, once for more than two hours.

“We haven’t found the aircraft yet and we need further confirmation,” he said, adding that this is 4,500 meters down.

The HMS Echo, a British navy ship equipped with advanced detection gear, sailed into the area of the southern Indian Ocean this morning where a Chinese crew had detected two audio signals, CNN reported.

And an Australian navy vessel carrying sophisticated US listening technology is investigating a sound it picked up in a different patch of the ocean.

Investigators hope the signals could be locator beacons from the plane’s data recorders, but they’re not sure yet.

It might be only a few hours before the pingers stop transmitting the signals as the batteries inside the beacons, which are designed to start sending signals when a plane crashes into water, last about 30 days after it’s activated.

Finding the black box is crucial to know what happened on March 8 before the Beijing—bound Malaysia Airlines jet with 239 people, including five Indians, disappeared under mysterious circumstances in midair.

The mystery of the missing plane continued to baffle aviation and security authorities who have so far failed to trace the aircraft despite deploying hi-tech radar and other gadgets.

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