China has urged Malaysia to step up its efforts in the hunt for the jetliner that mysteriously vanished on a flight to Beijing.
Authorities remain confounded by the disappearance of a Malaysia Airlines passenger jet with 239 people on board, as questions mount over possible security lapses.
Dozens of ships and aircraft from several countries, including New Zealand, have been searching the seas around Malaysia and south of Vietnam since flight MH370 vanished on its way to Beijing from Kuala Lumpur.
The Boeing 777-200 disappeared from radar screens in the early hours of Saturday, about an hour into its flight after climbing to a cruising altitude of 35,000 feet. Relatives of those aboard have been told to prepare for the worst.
China says it has deployed 10 satellites to help in the search. The People's Liberation Army Daily reported the satellites would use high-resolution earth imaging capabilities and other technologies.
Multinational rescue teams scoured an area stretching from the Malacca Strait to the South China Sea off Vietnam's coast on Tuesday. Vietnam says it is mobilising more ships and planes to join the search operation.
About two-thirds of the 227 passengers and 12 crew now presumed to have died were Chinese. The airline said other nationalities included 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans.
On the flight also were two New Zealanders - Ximin Wang, 50, from Auckland and described in the electoral roll as a student, and 38-year-old Paul Weeks, who was heading to Mongolia to start a job as a mining contractor.
Several potential clues as to what happened to the missing plane have been ruled out in the past day. Malaysia's civil aviation chief Azharuddin Abdul Rahman said analysis has shown an oil slick off Vietnam's coast did not contain fuel from the plane. A theory that a floating yellow object off Vietnam could have been a liferaft from the plane has also been discounted.
Tickets in fake names sold to Iranian - paper
Terrorism has not been ruled out, but there is a new line of investigation on two men who boarded the plane on fake passports and they are being linked to a stolen passport syndicate. Experts say their presence on the plane was a breach of security, but is relatively common in the region and could relate to illegal migration.
Police in Malaysia said one of the men travelling on a stolen passport was a young Iranian not thought to have terrorist links. They believe Pouria Nour Mohammad Mehrdad, 19, was travelling to Germany where he was hoping to seek asylum.
The Bangkok Post newspaper reports that tickets purchased on the flight by the men were issued by a Thai tour agency to an Iranian man. Thai police have confirmed the tickets were bought on Thursday in the Pattaya beach resort. The newspaper says someone collected them and paid for them in Thai baht.
The paper cites an unnamed employee at one of the tour agencies as saying both tickets were ordered via email by a man named "Ali" from Iran. It said the employee described Ali as a regular customer who had originally asked for tickets on Etihad Airlines or Qatar Airways flying to Copenhagen and Frankfurt, DPA reports.
The Bangkok Post said he later switched to China Southern Airlines, which has a code share agreement with Malaysia Airlines, because they were cheaper.
NZ Orion joins search
A massive air and sea search will be broadened on Tuesday and a New Zealand Orion will join the search for the plane.
The Defence Force says the plane has been refuelling in Darwin in Australia, and its crew resting, and will leave for Malaysia in the afternoon.
New Zealand Prime Minister John Key said while the Government is aware the hope for positive news is fading, its thoughts remain with the families of those on the flight, particularly the relatives of Paul Weeks and Ximin Wang.
Listen to more on Morning Report ( 5 min 34 sec )
Radar may have been off - expert
An aviation specialist told Radio New Zealand's Nine to Noon programme on Tuesday the missing plane may have kept flying with its radar off, or authorities may be withholding its radar-monitoring information.
Bill Waldock, a professor of safety science at Embry-Riddle Aeronautical University in Arizona, says much of the interior of the fuselage floats and should have been located.
"If there had been some sort of an in-flight explosion or some sort of an in-flight break-up, the searchers should have been able to find floating debris. If the airplane comes apart in flight, that's normally one of the first things you're gonna find. If it actually blew the airplane apart, it would have been close enough for land-based radars that would literally be able to see the various pieces of the airplane coming down."
Mr Waldock says if the plane's structure disintegrated, it would have been visible by radar almost all the way down to sea level.
Listen to full interview on Nine to Noon ( 14 min 31 sec )