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Trying to find a needle in a haystack while battling some of the roughest seas in the world, experts hunting for traces of missing Malaysia Airlines Flight MH370 are already facing a daunting task.

Their mission just got harder after they managed to lose a state-of-the-art piece of equipment — for the second time.

The search operation revealed details Wednesday of how it came to lose its second "towfish," an underwater sonar device dragged behind ships that scans the seabed for debris.

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The Remora III, the remotely-operated vehicle that will try to find and recover the lost towfish. Phoenix International

The yellow, torpedo-shaped unit was attached to an 1,800-pound weight to keep it floating from the surface when "the failure of a tow cable connector resulted in the loss of the … towfish and the attached depressor," the Joint Agency Coordination Centre (JACC) said in statement.

With the towfish likely thousands of feet down on the seabed, a remote-controlled submersible was flown in from the United States and dispatched aboard a ship from Australia on Monday, the JACC said.

Related: MH370 Search Will End This Summer, Official Says

It was the second time a towfish has been lost by the MH370 operation in less than three months.

In January, one of the devices was temporarily lost after it crashed into a 7,400-foot underwater volcano before being recovered around a week later.

A spokesman for the JACC told NBC News on Wednesday that the search operation has three towfishes and he was not sure whether the same device had been lost twice.

Map showing the progress of the underwater search for missing Flight MH370. Phoenix International

The enormous search operation has covered more than 38,000 square miles of a planned 46,000-square-mile search area — but it has not found a trace of the airliner that crashed on Mar. 8, 2014.

The Boeing 777 was carrying 239 passengers and crew when it disappeared from radar while flying from Kuala Lumpur to Beijing.