Search for Malaysian jet resumes off Australia after weather improves

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* Search resumes in southern Indian Ocean

* Chinese relatives clash with Beijing police, slam Malaysia

* Malaysia PM says MH370 crashed in southern Indian Ocean

* No hope of survivors

By Lincoln Feast and Megha Rajagopalan

SYDNEY/BEIJING, March 26 (Reuters) - The search for the Malaysian airliner that disappeared 18 days ago resumed on Wednesday in the southern Indian Ocean, looking for debris that may unlock the mystery of why the plane ended up in frigid seas thousands of miles off course.

A dozen aircraft from Australia, the United States, China, Japan and South Korea will scour the seas some 2,500 km (1,550 miles) southwest of Perth in the hunt for potential debris, the Australian Maritime Safety Authority said. Bad weather on Tuesday forced the suspension of the search.

Malaysian Prime Minister Najib Razak this week confirmed that Malaysia Airlines Flight MH370, which vanished while flying to Beijing from Kuala Lumpur, had crashed in the southern Indian Ocean.

Citing satellite-data analysis by British company Inmarsat (LSE: ISAT.L - news) , he said there was no doubt the Boeing (NYSE: BA - news) 777 came down in one of the most remote places on Earth - an implicit admission that all 239 people on board had died.

"We keep searching until there is absolutely no hope of finding anything," Australian Prime Minister Tony Abbott told Australia's Nine Network Television on Wednesday. "Plainly, there is quite a bit of debris in this part of the southern Indian Ocean. We've photographed it on a number of occasions now."

While numerous floating objects have been seen by satellite images and spotter planes in the search zone, none has been positively identified as coming from the missing jet.

Recovery of wreckage could unlock clues about why the plane had diverted so far off course. Theories range from a hijacking to sabotage or a possible suicide by one of the pilots, but investigators have not ruled out technical problems.

An Australian navy ship is returning to the area after being driven away by gale force winds and 20m (66ft) waves on Tuesday, while a Chinese icebreaker and other Chinese navy vessels are steaming towards the search zone.

PASSENGER RELATIVES DISTRAUGHT

Dozens of distraught relatives of Chinese passengers clashed with police in Beijing on Tuesday, accusing Malaysia of "delays and deception" in the search and investigation.

Malaysia's confused initial response to the plane's disappearance and a perception of poor communications has enraged many relatives of the more than 150 Chinese passengers and has strained ties between Beijing and Kuala Lumpur.

The United States said it was sending an undersea Navy drone to Australia, in addition to a high-tech black box detector, to help in the search.

The so-called black boxes - the cockpit voice recorder and flight data recorder - record what happens during flight, but time is running out to pick up locator beacons that stop about a month after a crash due to limited battery life.

The U.S. State Department said it was cooperating with Malaysia and working to verify the data from Inmarsat (Other OTC: IMASF - news) and the Kuala Lumpur government about the course of the U.S.-made plane.

"Basically, we are going back and looking at how they got to where they got to and seeing if our math experts and folks can get to the same place as well," State Department spokeswoman Marie Harf told a regular news briefing.

MULTINATIONAL INVESTIGATION

Flight MH370 vanished from civilian radar screens less than an hour after taking off on March 8 and investigators believe someone on the flight may have shut off the plane's communications systems.

Partial military radar tracking showed it turning west and recrossing the Malay Peninsula, apparently under the control of a skilled pilot.

The air crash investigation is shaping up as one of the most costly and difficult ever. Normally, an official investigation can only begin once a crash site has been identified. That would give Malaysia power to coordinate and sift evidence.

A government source told Reuters that Malaysia would lead the investigation, but hoped other countries, especially Australia, would play a major role. (Additional reporting by Ben Blanchard and Joseph Campbell in Beijing, Stuart Grudgings, Michael Martina, Siva Govindasamy and A. Ananthalakshmi in Kuala Lumpur; Phil Stewart and David Brunnstrom in Washington; Editing by Dean Yates)