In the search for Malaysia Airlines Flight 370, a plane has detected a possible signal from the locator beacons on the so-called black boxes from the missing aircraft, the Australian agency coordinating the search announced Thursday.

"The acoustic data will require further analysis overnight but shows potential of being from a man-made source," said retired Air Chief Marshal Angus Houston, the agency's chief coordinator.

The possible signal, which was picked up through sonar buoys equipped to receive such electronic data, was detected near the Australian ship Ocean Shield, said the Joint Agency Coordination Centre.

Crews have been narrowing the search area in the Indian Ocean.

Up to 10 military aircraft, four civil aircraft and 13 ships were to assist in Thursday's search for the Boeing 777-200ER, which was carrying 239 people when it vanished March 8 on a fight from Kuala Lumpur, Malaysia, to Beijing.

Three of the vessels - the Ocean Shield to the north, and the British HMS Echo and Chinese Haixun 01 to the south - were focusing underwater.

Aircraft and ships spotted a number of objects during Wednesday's search, but could recover only a small number, none of which appeared linked to MH370, the JACC said.

Thursday's search area is about 22,400 square miles (58,000 square kilometers), centered some 1,417 miles (2,280 kilometers) northwest of Perth. That's roughly the size of West Virginia.

But the latest search area is about three quarters of the size of the area that teams combed the day before and far smaller than what it was a few weeks ago.

We'll have the latest developments on this story on @ThisHour at 11am ET/ 8am PT.