Nearly 100 relatives and their supporters marched Tuesday to the Malaysian Embassy in Beijing, where they threw plastic water bottles, tried to rush the gate and chanted, "Liars!"
Many wore white T-shirts that read "Let's pray for MH370." They held banners and shouted, "Tell the truth! Return our relatives!"
Police briefly scuffled with a group of relatives who tried to approach journalists. The relatives demanded to see the Malaysian ambassador, and they later met with him.
In a clear statement of support for the families, Chinese President Xi Jinping ordered a special envoy, Vice Foreign Minister Zhang Yesui, to Kuala Lumpur to deal with the case. Deputy Foreign Minister Xie Hangsheng told Malaysia's ambassador that China wanted to know exactly what led Malaysian Prime Minister Najib Razak to announce that the plane had been lost, a statement on the ministry's website said.
The conclusions were based on an analysis of the brief signals the plane sent every hour to a satellite belonging to Inmarsat, a British company, even after other communication systems on the jetliner shut down for unknown reasons.
Yusof, the airline's chairman, said the conclusion was based on "the evidence given to us, and by rational deduction."
Investigators will be looking at various possibilities, including mechanical or electrical failure, hijacking, sabotage, terrorism or issues related to the mental health of the pilots or someone else on board.
"We do not know why. We do not know how. We do not know how the terrible tragedy happened," Malaysia Airlines' chief executive, Ahmad Jauhari Yahya, told reporters.
Australian and Chinese search planes spotted floating objects southwest of Perth on Monday, but none was retrieved. With the 24-hour delay in the search, those objects and other possible debris from the plane could drift to an even wider area.
There are 26 countries involved in the search, and Hishammudin said the problems are not diplomatic "but technical and logistical."
"We've got to get lucky," said John Goglia, a former member of the U.S. National Transportation Safety Board. "It's a race to get to the area in time to catch the black box pinger while it's still working."
Associated Press writers Todd Pitman in Kuala Lumpur; Christopher Bodeen, Ian Mader, Aritz Parra and Didi Tang in Beijing; Danica Kirka in London; and Kristen Gelineau in Sydney and Rod McGuirk in Canberra, Australia, contributed to this report.
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