KUALA LUMPUR (REUTERS) - The Malaysian authorities are investigating the identities of at least two other passengers on the missing Malaysia Airlines flight MH370, 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.