Authorities have yet to confirm the identities of two more European passengers on flight MH370, adding to two others using stolen passports in the Malaysia Airlines plane which vanished over the Malaysia-Vietnam maritime border yesterday.

The Malaysian Insider understands that all four had bought their flight tickets from China Southern Airlines, the Malaysia Airlines codeshare partner for the Kuala Lumpur-Beijing route.

"The background checks with the embassies are being done but these two cannot be confirmed," a source told The Malaysian Insider, adding that both were from the same country.

The Daily Telegraph's Beijing correspondent Malcolm Moore wrote in his Twitter microblog that the Chinese airline had sold seven tickets for the redeye flight, which carried 239 people, including 12 crew members, when it vanished.

More than half of the passengers, 153 to be exact, are Chinese nationals. There are 14 other nationalities on the Boeing 777-200 aircraft, including 38 Malaysians.

Malaysian authorities have downplayed the significance of those flying on stolen passports, with Deputy Transport Minister Datuk Abdul Aziz Kaprawi saying last night that they could not reveal too many details about security.

"We have reviewed the closed-circuit television video footage pertaining to passengers and their baggage.

"So far, we are satisfied with everything," Aziz said, adding that the authorities were not ruling out any possibilities at this juncture.

Malaysia Airlines chief executive officer Ahmad Jauhari Yahya cautioned against further speculation over those with suspect identities.

"These are reports which we need to form. As far as we are concerned, it is just a report.

"We are working foreign embassies to ensure we can confirm the report... Speculations have begun since this morning and every speculation has been squashed," he was quoted as saying by the Malaysiakini newsportal.

The Malaysia Airlines Boeing 777-200 departed Kuala Lumpur International Airport at 12.41am on Saturday and was expected to land in Beijing at 6.30am, a 3,700km journey but it never arrived.

An animated screenshot from Google Map shows the movement of the Malaysia Airlines flight MH370, which stopped somewhere at the South China Sea. – Image courtesy Daily Mirror, March 9, 2014. More

At the time of its disappearance, the Malaysia Airlines plane was carrying about 7½ hours of fuel, an airline official said.

The flag carrier, rated as one of the safest in the world, was piloted by a veteran, 53-year-old Captain Zaharie Ahmad Shah who has 18,365 flying hours and joined Malaysia Airlines in 1981.

The first officer is Fariq Ab Hamid, 27, who has 2,763 flying hours. He joined Malaysia Airlines in 2007.

The 11-year-old B777-200 for the flight is one of 15 in Malaysia Airlines' fleet.

CNN reported that if this aircraft has crashed with a total loss, it would the deadliest aviation incident since November 2001 when an American Airlines Airbus A300 crashed in Belle Harbor, Queens, shortly after takeoff from JFK Airport. Killed were 265 people, including five people on the ground. – March 9, 2014.