Ground staff take a break under a Malaysia Airlines plane at Kuala Lumpur International Airport in Sepang, Malaysia, Sunday, March 9, 2014. An international fleet of planes and ships scouted the waters between Malaysia and Vietnam for any clues to the fate of the Malaysia Airlines Boeing 777, which disappeared less than an hour after taking off from Kuala Lumpur bound for Beijing on Saturday, March 8. (AP Photo/Lai Seng Sin)

KUALA LUMPUR, March 9 (Reuters) - Malaysian authorities are investigating the identities of at least two other passengers on a missing Malaysia Airlines flight, in addition to two who were found to be using stolen passports, a security official said.

Investigators were verifying the identities with the relevant embassies in Malaysia, said the official, who has knowledge of the investigation and declined to be identified. The passengers being checked had all bought their tickets through China Southern Airlines, the official said.

The flight carrying 227 passengers and 12 crew was presumed to have crashed off the Vietnamese coast on Saturday, after losing contact with air traffic controllers off the eastern Malaysia coast.