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An underwater drone searching for missing Malaysia Airlines Flight 370 had to be recalled after suffering "communications problems" just hours after it was deployed, officials said Wednesday.

The Australian defense vessel Ocean Shield, carrying the U.S. Navy drone Bluefin-21, returned Tuesday to the site of the first and longest locator ping about 1,000 miles northwest of Perth, Australia.

"Work continues to rectify the issue and to date, Bluefin-21 has not redeployed," said a statement from the Australian government's Joint Agency Coordination Center, which is coordinating the search.

The searchers did not provide any details on what exactly the communications problems were.

The drone's first mission had been to investigate a 121-square-mile area around the shorter of the two locator pings heard on April 5. Experts hoped that these could have been emitted from the Boeing 777's black box recorder before it ran out of battery.

Like all other efforts to find the airliner that disappeared on March 8 en route from Kulala Lumpur and Beijng with 239 people on board the mission returned no clues.

The statement added that preparations were continuing for a "bathymetric survey" - which is a detailed study of the ocean floor and would form the basis for the next stage in the search.

- Alexander Smith