By KEITH BRADSHER
New York Times
MARCH 8, 2014

HONG KONG — As searchers scoured the Gulf of Thailand early Sunday for a Malaysia Airlines jet with 239 people aboard, investigators examined the usual causes of such disappearances: bad weather, possible mechanical failures, pilot error. But the discovery that at least two passengers were carrying stolen passports also raised the unsettling possibility of foul play.

As of the predawn hours Sunday, there was little to go on: no wreckage of the jet, a Boeing 777-200 on a red-eye flight from Kuala Lumpur, Malaysia to Beijing, had been found, and other than a 12-mile-long oil slick on the surface of the gulf, there was no hint that a crash had even taken place.

Officials stressed that the investigation was in its earliest stages and that they were considering all possibilities. The airline said the plane had recently been inspected and had no history of malfunctions. Malaysia’s deputy minister of transport, Aziz bin Kaprawi, said the authorities had received no distress signal from the aircraft.

But limits of the fuel tanks board the jet on Flight MH 370 meant that it came down somewhere instead of reaching Beijing at dawn on Saturday as scheduled If it did end up in the Gulf of Thailand , rescuers would have one advantage:the gulf is a shallow arm of the South China Sea, with no comparison to the inky depths of the Atlantic.

Officials in Vienna and Rome confirmed that the names of two citizens, an Italian and an Austrian, listed on the manifest of the missing flight matched the names on two passports that were reported stolen in Phuket, Thailand.

A European counterterrorism official said the passport of the Italian man, whom the official identified as Luigi Maraldi, had been stolen at a vehicle rental shop in Phuket on Aug. 1. The official said the passport of the Austrian man, Christian Kozel, was stolen two years ago.

A senior American intelligence official said law enforcement and intelligence agencies were investigating the matter. But so far, they had no leads.

“At this time, we have not identified this as an act of terrorism,” said the official, who spoke on the condition of anonymity because of the continuing inquiry. “While the stolen passports are interesting, they don’t necessarily say to us that this was a terrorism act.”

The European counterterrorism official, who also declined to be publicly identified discussing an ongoing investigation, said he was “surprised that it was possible to check-in with stolen passports in Kuala Lumpur.”

“Normally this should not be possible,” he said, adding: “I think this should be checked thoroughly. Maybe they were careless – or somebody helped them.”

The chief executive of Malaysia Airlines, Ahmad Jauhari Yahya, told reporters at Kuala Lumpur International Airport on Saturday night: “We are not ruling out anything. As far as we are concerned right now, it’s just a report.”

Xinhua, the Chinese state news agency, reported that the Chinese prime minister, Li Keqiang, held an urgent telephone call with his Malaysian counterpart, Najib Razak, telling him, “The urgent task now is to quickly clarify the situation, and use a range of means to enhance the intensity of search and rescue.”

Malaysia Airlines said the plane had 227 passengers aboard, including two infants, and an all-Malaysian crew of 12. The passengers included 154 citizens from China or Taiwan, 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans, as well as two citizens each from Canada, New Zealand and Ukraine and one each from Austria, Italy, the Netherlands and Russia.

Among the Americans was Philip Wood, an IBM employee in Kuala Lumpur, whose family lives in Texas.

Malaysia, the United States and Vietnam dispatched ships and aircraft to the mouth of the Gulf of Thailand on Saturday to join an intensive search. China said it had sent a vessel to the area at top speed that would arrive there on Sunday afternoon.

Lai Xuan Thanh, the director of the Civil Aviation Administration of Vietnam, said a Vietnamese Navy AN26 aircraft had discovered the oil slick toward the Vietnam side of the mouth of the Gulf of Thailand.

Fredrik Lindahl, the chief executive of Flightradar24, an online aircraft tracking service, said the missing plane had been equipped with a transponder that regularly transmitted its position via GPS satellites. The last recorded position of Flight MH370 was 93 miles northeast of Kuala Terengganu, a port on the northeast coast of Peninsular Malaysia, he wrote in an email.

Mr. Ahmad of Malaysia Airlines said in a statement that there had been speculation that the plane landed safely somewhere along the route to Beijing, and said the airline was investigating. But in a telephone interview before reporting the sighting of the slick, Mr. Lai expressed concern about the aircraft’s fate.

“The possibility of an accident is high,” he said.

Relatives of those on the missing flight who were waiting at Beijing Capital International Airport were taken to a hotel and kept waiting in a room for hours, prompting complaints. One woman said no one from Malaysia Airlines had come to the room to talk to relatives.

Liu Meng, 26, who works for a communications company, said he had been waiting for his boss to arrive from Malaysia since 6 a.m. “I was able to contact him up until yesterday afternoon,” Mr. Liu said. “After that, nothing.”

At the Kuala Lumpur airport, a grief-stricken relative of a passenger aboard MH370 screamed uncontrollably as he was escorted out of the terminal by airline employees.

“Be truthful about this!” said the man, Koon Chim Wa, whose booming voice echoed through the cavernous terminal.

“They say they don’t know where the plane is,” Mr. Koon said, his hands and body shaking. “Is this a joke?”

Lt. Col. Pham Hong Soi, the head of the propaganda department of the Vietnam Navy for the region near the crash site, said one rescue vessel had already been ordered to sea and two more were ready for departure.

Malaysia’s prime minister, Mr. Najib, said in a statement that 15 aircraft and nine ships were searching for the missing plane. Without saying where his government suspected that the plane disappeared, he added, “Our priority now is to widen the search area and provide support to relatives of those missing.”

The United States Seventh Fleet said it was sending a destroyer, the Pinckney, and a P-3C maritime surveillance aircraft to join the search for Flight MH370.

In addition, the Chinese State Oceanic Administration said it had sent a Coast Guard ship to the area where the plane might have gone down. “It is traveling at full speed to the waters, and is expected to reach there on the afternoon of the 9th,” said a statement on the administration’s website.

The Chinese Ministry of Transport said a team of scuba divers who specialize in emergency rescues and recovery had been assembled on Hainan, the southern island-province, to prepare to go on Sunday to the area where the where airliner may have gone down.

China Central Television said that according to Chinese air traffic control officials, the aircraft never entered Chinese airspace.

Boeing said in a statement that it was assembling a team of technical experts to advise the national authorities investigating the disappearance of the aircraft.

One uncertainty about the flight involved the timing of its disappearance from radar. Malaysia Airlines said it took off at 12:41 a.m. Malaysia time and disappeared from air traffic control radar in Subang, a suburb of Kuala Lumpur, at 2:40 a.m.

That timeline seemed to suggest that the plane stayed in the air for two hours — long enough to fly not only across the Gulf of Thailand but also far north across Vietnam. But Mr. Lindahl of Flightradar 24 said that the last radar contact had been at 1:19 a.m., less than 40 minutes after the flight began.

A Malaysia Airlines spokesman said on Saturday evening that the last conversation between the flight crew and air traffic control in Malaysia had been around 1:30 a.m., but he reiterated that the plane had not disappeared from air traffic control systems in Subang until 2:40 a.m.

Arnold Barnett, a longtime Massachusetts Institute of Technology specialist in aviation safety statistics, said that before the disappearance of the plane, Malaysia Airlines had suffered two fatal crashes, in 1977 and 1995. Based on his estimate that Malaysia Airlines operates roughly 120,000 flights a year, he calculated that the airline’s safety record was consistent with that of airlines in other fairly prosperous, middle-income countries but had not yet reached the better safety record of airlines based in the world’s richest countries.

Malaysia, near the Equator, is a popular winter vacation destination for affluent residents of chilly, smoggy Beijing.

The list of Chinese passengers aboard the missing flight included the names of artists who had attended a meeting in Kuala Lumpur, said the newspaper Beijing News. Other reports said the missing included members of a returning delegation of Buddhists.

If the plane is confirmed to have crashed into the sea, the disaster would add to a difficult week for China and its government. Last Saturday, a group of assailants used knives and daggers to kill 29 people and wound more than 140 at a train station in Kunming, a city in southwest China.

China’s growing wealth has brought a steep rise in the number of its citizens traveling overseas, especially throughout Asia, and the government has sometimes faced allegations, especially from Internet users, that officials failed to adequately help victims of emergencies abroad and their families. This time, President Xi Jinping of China and other senior officials swiftly issued statements to show they were closely following developments.

Correction: March 8, 2014

Because of an editing error, an earlier version of this article referred incorrectly, on second reference, to the chief executive officer of Malaysia Airlines, Ahmad Jauhari Yahya. He is Mr. Ahmad, not Mr. Yahya.

Reporting was contributed by Thomas Fuller from Kuala Lumpur, Malaysia; Eric Schmitt from Washington; Chau Doan from Hanoi, Vietnam; Amy Qin from Beijing; Chris Buckley from Hong Kong; and Alison Smale from Berlin. Bree Feng contributed research from Beijing.