The search for a missing Malaysia Airlines jetliner resumed on Saturday, five weeks after the plane disappeared from radar screens, amid fears that batteries powering signals from the black box recorder on board may have died.

Australian Prime Minister Tony Abbott warned on Friday that signals picked up during the search in the remote southern Indian Ocean, believed to be “pings” from the black box recorders, were fading.

Malaysia Airlines Flight MH370 disappeared soon after taking off on March 8 from Kuala Lumpur bound for Beijing with 227 passengers and 12 crew on board, triggering a multinational search that is now focused on the Indian Ocean.

Search officials say they are confident they know the approximate position of the black box recorder, although they have determined that the latest “ping”, picked up by searchers on Thursday, was not from the missing aircraft.

Batteries in the black box recorder are already past their normal 30-day life, making the search to find it on the murky sea bed all the more urgent.