An Austrian, whose name was also on the boarding list, had his passport stolen as well. The Austrian foreign ministry said the man was safe at home.
A statement by Malaysian acting Transport Minister Hishammuddin Hussein said the authorities are looking at four possible cases of suspected identities.
In a statement, Malaysia Airlines said it feared the worst for the missing plane.
"...A disaster recovery management specialist from Atlanta, US, will be assisting Malaysia Airlines in this crucial time," the airline said.
It disclosed the missing plane's wingtip was repaired by Boeing before returning to fly.
China also sent an emergency response team Sunday morning to find the plane.
A team assembled by the Chinese transport ministry set out from the Sanya port in Hainan province to the South China Sea area where the flight may have plunged, Xinhua reported.
Rescue vessel "South China Sea Rescue 101" with 12 divers and salvagers will join another rescue vessel "South China Sea Rescue 115" at the site.
Sanya port is 700 sea miles from the possible crash site. Both the rescue vessels have helipads which enable air search.
As of 1 p.m. Sunday, another vessel "China Coast Guard 3411" entered the waters in the vicinity of the spot where the plane was believed to have been when it lost contact with ground control, according to China's State Oceanic Administration.
