KUALA LUMPUR/PHU QUOC, Vietnam - The search for a missing Malaysia Airlines jetliner expanded on Wednesday to cover a swathe of Southeast Asia, from the South China Sea to India's territorial waters, with authorities no closer to explaining what happened to the plane or the 239 people on board.

Vietnam briefly scaled down search operations in waters off its southern coast, saying it was receiving scanty and confusing information from Malaysia over where the aircraft may have headed after it lost contact with air traffic control.

Special: Malaysia Airlines plane missing

Hanoi later said the search - now in its fifth day - was back on in full force and was even extending on to land. China also said its air force would sweep areas in the sea, clarifying however that no searches over land were planned.

The seas off India's Andaman and Nicobar Islands are also being combed for traces of the lost jet.

"We are expanding to the east of the expected route of the flight and on land," Lieutenant General Vo Van Tuan, Vietnam's deputy army chief of staff and spokesman for its search and rescue committee, told reporters.

The confusion over where to look is adding to one of the most baffling mysteries in modern aviation history, and prolonging the agonising wait for hundreds of relatives of the missing.

Flight MH370 dropped out of sight an hour after taking off from Kuala Lumpur to Beijing early on Saturday, under clear night skies and with no suspicion of any mechanical problems.

Dozens of planes and ships have already searched tens of thousands of square miles of Malaysia and off both its coasts without finding a trace of the Boeing 777.

Adding to the frustration and uncertainty, Malaysia's military has said the plane could have turned around from its planned flight path, but there were conflicting statements and reports about how far and in which direction it could have flown after communication was lost.