The mystery over the plane's whereabouts has been confounded by confusing and occasionally conflicting statements by Malaysian officials, adding to the anguish of relatives of the 239 people on board the flight.
An international search mission for the Malaysian Airlines plane, which disappeared on Saturday, is continuing.
Two-thirds of those on board were Chinese and Chinese Foreign Ministry spokesman Qin Gang said: "There's too much information and confusion right now. It is very hard for us to decide whether a given piece of information is accurate. We will not give it up as long as there's still a shred of hope."
Malaysian Defence Mminister Hishammuddin Hussein described the multi-national search for the missing plane as an unprecedented and complicated situation and defended his country's efforts.
Some 43 ships and 39 aircraft from at least eight nations are scouring an area of 35,800sq miles.
Mr Hishammuddin said: "It's not something that is easy. We are looking at so many vessels and aircraft, so many countries to co-ordinate and a vast area for us to search. But we will never give up. This we owe to the families."
Malaysia Airlines flight 370 took off from Kuala Lumpur for Beijing early on Saturday morning and disappeared from civilian radar screens at 1.30am, about 35,000ft above the Gulf of Thailand between Malaysia and southern Vietnam. It sent no distress signals or any indication it was experiencing problems.
Malaysian authorities have since said air defence radar picked up traces of what might have been the plane turning back and flying until it reached the Strait of Malacca, a busy shipping lane west of the narrow nation 250 miles from the plane's last known co-ordinates.
Military and government officials said American experts, and the manufacturer of the radar systems, were examining that data to confirm it showed the Boeing 777. Until then, they said the search would continue on both sides of the country, with an equal focus.
Dozens of ships and planes searching waters have failed to turn up anything as yet, prompting officials to expand the hunt.
Malaysia has asked India to join the search for the missing jet in waters near the Andaman Sea - far to the north-west of its last reported position.
Mr Hishammuddin praised India for joining the efforts and vowed to keep up the search until the plane was found.
Air force chief Gen Rodzali Daud said air defence radar showed an unidentified object at 2.15am on Saturday about 200 miles north-west of Penang. He added: "I am not saying it's flight MH370. We are still corroborating this. It was an unidentifiable plot."
Authorities have not ruled out any possible cause, including mechanical failure, pilot error, sabotage or terrorism. Both the Boeing 777 and Malaysia Airlines have excellent safety records. Until wreckage or debris is found and examined, it will be very hard to say what happened.
Mr Hishammuddin said his government had been transparent from the start.