Missing Malaysian airlines flight and terror strike probe
A military aircraft (top) lands in hazy weather at the Tan Son Nhat airport in Ho Chi Minh cityReuters

Authorities are investigating the reported presence of at least two and not four suspects aboard the missing Malaysia Airlines MH370 flight as US intelligence agencies, including the FBI, are set to join the probe over the Boeing 777's mysterious disappearance.

Malaysian officials have clarified the CCTV footage indicate there were only two imposters who are believed to have travelled with fake IDs.

"There are only two passengers on record on this aircraft with false passports and we have the CCTV recordings of those passengers from check in, right to the departure point and this record of the CCTVs are now being used in investigations on this," said the director-general of Department of Civil Aviation, Datuk Azharuddin Abdul Rahman.

Alongside the two suspects, the Malaysian authorities are scanning the entire passenger manifest in detail as the plane or its wreckage remains untraced.

Earlier at a press conference, Malaysia's acting transport minister Datuk Seri Hishammuddin Hussein told reporters at the Kuala Lumpur International Airport (KLIA). "We are investigating the entire manifest, not just the four passengers. The disappearance of MH370 is not something which can be taken lightly and we cannot discount any possibilities. The intelligence agencies of relevant countries have been informed and we will be sharing information as investigations unfold."

"Following discussions, intelligence agencies of various countries have agreed to work together to check the passenger manifest and the stolen passports. How the four individuals managed to board MH370 with stolen passports is being discussed. However, this is an international network and we cannot completely blame the Immigration Department."

It was earlier reported that two passengers boarded the flight with stolen passports fuelling the current speculation over a terrorism angle to the plane's disappearance.

When asked whether it was a security lapse, the transport minister stopped short of admitting it and insisted it needs to be ascertained. He said it is still uncertain whether the aircraft, with 239 people aboard, was brought down in the South China Sea by an attack.

The search for the vanished aircraft continues as ships and jets are being scrambled from across the southeast nations including Vietnam, Malaysia, and Singapore. Though two possible oil slicks have been spotted in the South China Sea by Vietnamese forces, there has been no evidence so far to link them with the aircraft's disappearance.

The Kuala Lumpur-Beijing flight has been missing for more than 24 hours now. There were 227 passengers of 14 different nationalities, the majority of them Chinese.