BEIJING — An international hunt for clues in the disappearance of a Malaysia Airlines passenger jet intensified Monday, with dozens of ships searching a vast expanse of sea and investigators chasing down leads. But authorities acknowledged that they were stymied.
"This unprecedented missing aircraft mystery — as you can put it — it is mystifying," Azharuddin Abdul Rahman, director general of Malaysia's Department of Civil Aviation, said at a news conference in Kuala Lumpur.
The U.S. Navy dispatched a second ship Monday to assist an emergency operation in the Gulf of Thailand and South China Sea that has grown to involve at least 40 other vessels and 34 aircraft from 10 countries. But as in the previous two days of searching, no wreckage from Malaysia Airlines Flight MH370 appeared.
In Thailand, officials interviewed travel agents in the beach resort of Pattaya, where tickets were apparently issued for two men who later boarded the flight with stolen passports, according to the Associated Press. The two men's fake identities had raised the possibility that a terrorist attack brought down the Boeing 777, which was carrying 227 passengers from Kuala Lumpur to Beijing when it vanished Saturday.
But U.S. and other officials say they have found no evidence of terrorist involvement.
Senior American officials dismissed reports that a group called the Chinese Martyrs' Brigade had asserted responsibility for the plane's disappearance.
In a vacuum of evidence about what went wrong aboard the flight, speculation turned to the possibility of pilot suicide, an extraordinarily rare occurrence.
"You have to ask the question," said a U.S. aviation official who was not authorized to discuss the matter publicly.
The Malaysia Airlines flight reportedly was being tracked by radar when its transponder went dark. There were no radio transmissions to indicate anything was amiss aboard the plane. The transponder signals and radio communication are controlled by the pilot.
There have been two cases in recent years in which a pilot or crew member is believed to have intentionally caused a plane to crash: the disaster involving SilkAir Flight 185, which spiraled into the ground in Indonesia in 1997, killing 97 passengers and seven crew members; and the crash of EgyptAir Flight 990, which plunged into the Atlantic south of Nantucket in 1999, killing 217 people.
But Steve Marks, a Miami aviation lawyer who represented families in two instances in which an airliner plummeted from cruising altitude, pointed to a mechanical failure as the most likely cause of the Malaysia tragedy.
"There can be a mechanical problem that can occur at altitude, where the pilots are unable to report the failure and the aircraft is lost on radar," he said. Nonetheless, he said, the failure of all communications from the Malaysia Air flight made it "the most mysterious" crash in his recollection.