The unprecedented hunt for a missing Malaysia Airlines jet is continuing 10 days after it vanished. A summary of the latest information on the search for the plane and the investigation into what happened:
Chinese authorities say they have checked into the background of all Chinese nationals on board the missing Boeing 777 jetliner but have uncovered no links to terrorism or any evidence to suggest they were involved in hijacking, according to Huang Huikang, the Chinese ambassador in Kuala Lumpur.
The finding dampens speculation that Uighur separatists in China's far western Xinjiang province might have been involved with plane's disappearance. Of the 239 passengers and crew aboard when the plane disappeared on March 8, 154 were Chinese.
For now, Malaysian authorities believe someone on board the flight intentionally switched off two vital pieces of communication equipment and deliberately diverted the aircraft. That could only have been done by the pilots -- either willingly or forced -- or someone on board with considerable flying experience.
Malaysian police are investigating the two pilots and ground engineers, and analyzing a flight simulator seized from the pilot's home.
Investigators are also checking backgrounds, including those of ground crew who could have come into contact with the plane, to see if links to terrorists, personal problems or psychological issues could be factors.
China says it has begun using satellites to scan its territory for the missing plane after satellite data indicated the jet's last position could be anywhere along two sections of a vast arc stretching from Central Asia to the southern reaches of the Indian Ocean. China also sent naval ships that had been in the South China Sea to the Indian Ocean.
Malaysian Defense Minister Hishammuddin Hussein said that the search area in the northern and southern "corridors" totals 2.24 million square nautical miles (nearly 3 million square miles), or 7.7 million square kilometers. That's about the size of Australia. Twenty-six countries are involved in the hunt.
Given the shift to the much wider search area, the U.S. Navy says that it will use long-range naval aircraft to look for the plane, and send its destroyer, the USS Kidd, back to normal duties. Australia is leading the search efforts in the southern Indian Ocean.
The northern search corridor includes countries with busy airspace that likely would have noticed an unidentified aircraft in their territory. China, India and Pakistan are among the nations that say they have seen no sign of the plane.
Beyond the question of where the plane is, many unknowns remain. Investigators are also considering: If the two pilots were involved in the disappearance, were they working together or alone, or with one or more of the passengers or crew? Did they fly the plane under duress or of their own will?
Did one or more of the passengers manage to break into the cockpit or use the threat of violence to gain entry and then seize the plane? And what possible motive could there be for diverting the jet?