A check of documents used by passengers to board a missing Malaysia Airlines flight has identified suspect passports that require further investigation, an Interpol spokeswoman said on Sunday.

"We have been checking all the passports and there are some which are requiring further investigation. These are the suspect passports," a spokeswoman for the international police agency said.

Two passports used to board the Beijing-bound plane, which disappeared after takeoff from Kuala Lumpur early on Saturday, were used by unknown persons after being stolen from their Italian and Austrian owners.