KUALA LUMPUR, Malaysia » China demanded Tuesday that Malaysia turn over the satellite data used to conclude that a Malaysia Airlines jetliner had crashed in the southern Indian Ocean, killing all 239 on board. Officials sharply narrowed the search area as a result of that assessment, but the zone remains as large as Texas and Oklahoma combined.

Australia said improved weather would allow the hunt for the plane to resume Wednesday after gale-force winds and heavy rain forced a daylong delay. Searchers face a daunting task of combing a vast expanse of choppy seas for suspected remnants of the aircraft sighted earlier.

"We’re not searching for a needle in a haystack — we’re still trying to define where the haystack is," Australia’s deputy defense chief, Air Marshal Mark Binskin, told reporters at a military base in Perth as idled planes stood behind him.

Late Monday, Malaysian Prime Minister Najib Razak announced that a new analysis of satellite data confirmed the plane had crashed in a remote part of the southern Indian Ocean.

That announcement unleashed a storm of sorrow and anger among the families of the plane’s passengers and crew — two-thirds of them Chinese. Family members of the passengers have complained bitterly about a lack of reliable information and some say they are not being told the whole truth.

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" as they held banners and shouted, "Tell the truth! Return our relatives!"

There was a heavy police presence at the embassy. Police briefly scuffled with a group of relatives who tried to approach journalists.

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 Najib to announce that the plane had been lost, a statement on the ministry’s website said.

Investigators and the Malaysian government have been able to say little with certainty about Flight 370’s fate since it disappeared on March 8 shortly after taking off from Kuala Lumpur for Beijing.

Left unanswered are many troubling questions about why it was so far off course. Experts piecing together radar and satellite data believe the plane back-tracked over Malaysia and then traveled in the opposite direction to the Indian Ocean.

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.

The airline’s chairman, Mohammed Nor Mohammed Yusof, said Tuesday it may take time for further answers to become clear.

"This has been an unprecedented event requiring an unprecedented response," he said. "The investigation still underway may yet prove to be even longer and more complex than it has been since March 8th."

He added that even though no wreckage has been found, there was no doubt the plane had crashed.

"This by the evidence given to us, and by rational deduction, we could only arrive at that conclusion: That is, for Malaysia Airlines to declare that it has lost its plane, and by extension, the people in the plane," he 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.

The latest satellite information does not provide an exact location but just a rough estimate of where the jet crashed into the sea.

Hishammuddin said the data is still being analyzed "to attempt to determine the final position of the aircraft" and that an international working group of satellite and aircraft performance experts had been set up. He did not give more details.

The search area has been reduced as a result of the new data to 1.6 million square kilometers (622,000 square miles), a massive expanse of ocean, but just 20 percent of the area that was previously being searched, he said.

There had been two corridors — based on rough satellite data — for the search. Hishammuddin said operations had been halted in the northern corridor that swept up from Malaysia toward Central Asia, as well as in the northern section of the southern corridor that arches down from Malaysia toward Antarctica.

Although there have been an increasing number of apparent leads, there has been no confirmed identification of any debris.

Australian and Chinese search planes spotted floating objects in an area 2,500 kilometers (1,550 miles) southwest of Perth on Monday, but none was retrieved. Now, with the 24-hour delay in the search, those objects and other possible debris from the plane could drift to an even wider area.

"A visual search will resume tomorrow when the weather is expected to improve after gale-force winds and heavy swells resulted in the suspension of the search operation on Tuesday," said the Australian Maritime Safety Authority, which is overseeing the search out of Perth, Australia.

There is a race against the clock to find any trace of the plane that could lead searchers to the black boxes, whose battery-powered "pinger" could stop sending signals within two weeks. The batteries are designed to last at least a month.

Several countries have begun moving specialized equipment into the area to prepare for a search for the plane and its black boxes, the common name for the cockpit voice and data recorders, needed to help determine what happened to the jetliner.

Hishammuddin said a U.S. Navy deep-sea black box locator was on its way to Australia and would be installed on an Australian navy support vessel, the Ocean Shield, which is expected to arrive in several days. It is not expected to reach the search area until April 5.

There are 26 countries involved in the search, and Hishammudin said the problems now facing the hunt to recover Flight 370 are not diplomatic "but technical and logistical."

The U.S. Navy has also sent an unmanned underwater vehicle to Perth that could be used if debris is located, said Rear Adm. John Kirby, a Pentagon spokesman.

Australian Prime Minister Tony Abbott said he had spoken to Najib to offer help with the ongoing search and investigation.

"What up until now has been a search, moves into a recovery and investigation phase," Abbott said. "I have offered Malaysia, as the country legally responsible for this, every assistance and cooperation from Australia."

The search for the wreckage and the plane’s recorders could take years because the ocean is up to 7,000 meters (23,000 feet) deep in some parts. It took two years to find the black box from an Air France jet that went down in the Atlantic Ocean on a flight from Rio de Janeiro to Paris in 2009, and searchers knew within days where the crash site was.

"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."

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Associated Press writers Todd Pitman in Kuala Lumpur; Christopher Bodeen, Ian Mader, Aritz Parra and Didi Tang in Beijing; Cassandra Vinograd in London; Darlene Superville in Washington; and Kristen Gelineau in Sydney and Rod McGuirk in Canberra, Australia, contributed to this report.