Officials investigating the disappearance of the Malaysian flight MH-370 believe the final voice transmission was made before communications systems were cut off.

That suggests the last words heard were from the pilots themselves and not any form of interception.

Intensive background checks on people on the missing plane have so far failed to find anyone with a known motive to hijack the plane.

The search for the aircraft has now been expanded to an area of around 10 million miles.