Vietnamese authorities searching waters for the missing Malaysia Airlines flight have spotted an object that they suspect to be one of the plane's doors.

Meanwhile, international police agency Interpol has confirmed that at least two passports, recorded in its Stolen and Lost Travel Documents database, were used by passengers on board the flight MH 370. The agency added that it was examining additional suspect passports.

In a statement, Interpol said the two passports, from Austria and Italy, were added to their database after they were stolen in Thailand in 2012 and 2013. But since no country made any checks of the passports before the departure of flight MH 370, Interpol says it's unable to determine on how many occasions they have been used.

The security agency is currently in contact with its National Central Bureaus in the involved countries, to determine the true identities of the passengers who used the passports.

Interpol Secretary General Ronald Noble says they are making all resources available to help authorities find out what happened.