The undersea search for wreckage from MH370, the airliner that disappeared over Asian waters a year ago, will go on through the end of May, Malaysia's transport minister says. But, if nothing turns up by then, the effort to learn the fate of the Boeing 777 goes "back to the drawing board," he says.

Speaking on the eve of the one-year anniversary of the plane's disappearance on March 8, 2014, Liow Tiong told reporters in the Malaysian capital, Kuala Lumpur: "By the end of May, if we still can't find the plane, then we will have to go back to the drawing board."

The fate of the flight, which vanished with 239 passengers and crew aboard en route from Kuala Lumpur to Beijing, has been the subject of intense speculation and multiple conspiracy theories.

"It's too early to pre-empt anything now," Liow was quoted by The Associated Press as saying of the search, which has been focused for months on an area far off the west coast of Australia in the turbulent southern Indian Ocean.

"I am cautiously optimistic it should be in this area," Liow said, according to the AP. "[We] need directions, we need plans, we need to review all the data that we have," he said.

Liow said 44 percent of a 23,000-square-mile search area in the Southern Ocean has been scanned. He said that so far, 10 hard objects had been detected on the ocean floor that have yet to be thoroughly analyzed.

"We are confident we can complete the search hopefully by May this year, and we hope we can get the plane," Liow said.

The director of Malaysia's Department of Civil Aviation says it has been difficult for his agency to fend off the false perception that it is hiding information.

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