KUALA LUMPUR, Malaysia - A Malaysia Airlines Boeing 777-200 carrying 239 people lost contact with air traffic control early Saturday morning on a flight from Kuala Lumpur to Beijing.
Vietnamese media reported that authorities detected signals from a missing Malaysia Airlines flight off the southwestern coast of Vietnam on Saturday, hours after the flight went missing during a flight from Kuala Lumpur to Beijing.
Website VN Express said a Vietnamese search and rescue official reported that the signals were detected from about 120 nautical miles (140 miles) southwest of Vietnam's southernmost Ca Mau province.
The airlines said four U.S. citizens, including one infant were on board.
The plane lost communication two hours into the flight over Vietnam at 1:20 a.m. (18:20 GMT Friday), China's state news agency said. The radar signal also was lost, Xinhua reported.
There were rumors the plane had landed safely, but Fuad Sharuji, Malaysian Airlines' vice president of operations control, told CNN that they were untrue and the airline had no idea where the plane was. Air Asia CEO Tony Fernandes sent a tweet saying that the radio failed and all were safe, but the tweet was later deleted.
Sharuji said that the plane was flying at an altitude of 35,000 feet and that the pilots reported no problem with the aircraft.
Flight MH370 departed Kuala Lumpur at 12:41 a.m. Saturday and was expected to land in Beijing at 6:30 a.m. Saturday, Malaysia Airlines said.
The plane was carrying 227 passengers, including two infants, and 12 crew members, the airline said.
The airline said it was working with authorities who activated their search and rescue teams to locate the aircraft. The route would take the aircraft from Malaysia across to Vietnam and China.
"Our team is currently calling the next-of-kin of passengers and crew. Focus of the airline is to work with the emergency responders and authorities and mobilize its full support," Malaysia Airlines CEO Ahmad Jauhari Yahya said in a statement.
"Our thoughts and prayers are with all affected passengers and crew and their family members," he added.
At Beijing's airport, Zhai Le was waiting for her friends, a couple, who were on their way back to the Chinese capital on the flight. She said she was very concerned because she hadn't been able to reach them.
Airport authorites posted a written notice asking relatives and friends of passengers to gather to a hotel about 30 minutes drive from the airport to wait for further information, and provided a shuttle bus service.
Another woman wept aboard the shuttle bus while talking by mobile phone, " They want us to go to the hotel. It cannot be good!"
Malaysia Airlines has 15 Boeing 777-200 jets in its fleet of about 100 planes. The state-owned carrier last month reported its fourth straight quarterly loss.
The 777 had not had a fatal crash in its 20 year history until the Asiana crash in San Francisco in July 2013. All 16 crew members survived, but thee of the 291 passengers, all teenage girls from China, were killed.
Associated Press writers Chris Brummitt in Hanoi, Vietnam, Didi Tang and video producer Aritz Parra in Beijing, China, contributed to this report.