Vietnamese air force planes on Saturday spotted two large oil slicks in the area where a Malaysia Airlines Boeing 777 vanished earlier in the day, the first sign that the aircraft carrying 239 people on board had crashed.

The air force planes were part of a multinational search operation launched after Flight MH370 fell off radar screens less than an hour after it took off from Kuala Lumpur for Beijing early Saturday morning.

A Vietnamese government statement said the slicks were spotted late Saturday off the southern tip of Vietnam and were each between 10 kilometres and 15 kilometres long. There was no confirmation that the slicks were related to the missing plane, but the statement said they were consistent with the kinds that would be produced by the two fuel tanks of a crashed jetliner.

Nationality of passengers

  • China/Taiwan: 154 including infant.
  • Malaysia: 38.
  • India: 5
  • .Indonesia: 7.
  • Australia: 6.
  • France: 4.
  • United States: 3 including infant.
  • New Zealand: 2.
  • Ukraine: 2.
  • Canada: 2.
  • Russian :1.
  • Italy: 1.
  • Netherlands: 1.
  • Austrian: 1

Source: Malaysia Airlines statement

Two-thirds of the missing plane's passengers were from China, while others were from elsewhere in Asia, North America and Europe.

Malaysia Airlines CEO Ahmad Jauhari Yahya said there was no indication that the pilots sent a distress signal. The fact that there was apparently no call for help suggests that whatever happened to the flight occurred quickly.

At Beijing's airport, authorities posted a notice asking relatives and friends of passengers to gather at a hotel about 15 kilometres from the airport to wait for further information, and provided a shuttle bus service. A woman wept aboard the shuttle bus while saying on a mobile phone, "They want us to go to the hotel. It cannot be good!"

"There is very little optimism," CBC's Andrew Lee reported from Beijing. "The mourning is happening right now. However, there is still hope for closure as the search continues."

Relatives and friends of passengers were escorted into a private area at the Lido Hotel, and reporters were kept away. A man in a grey hooded sweatshirt later stormed out complaining about a lack of information. The man, who said he was a Beijing resident but declined to give his name, said he was anxious because his mother was on board the flight with a group of 10 tourists.

"We have been waiting for hours," he said. "And there is still no verification."

The plane was last detected on radar at 1:30 a.m. local time about 135 kilometers north of the Malaysian city of Kuala Terengganu, said Azaharudin Abdul Rahman, Malaysia's civil aviation chief.

Lai Xuan Thanh, director of Vietnam's civil aviation authority, said air traffic officials in the country never made contact with the plane. The plane "lost all contact and radar signal one minute before it entered Vietnam's air traffic control," Lt. Gen. Vo Van Tuan, deputy chief of staff of the Vietnamese army, said in a statement.

Regional differences put aside

Although it would be hard to determine what conditions were like in the jet stream, CBC meteorologist Johanna Wagstaffe said there was some haze on the ground in Vietnam and a few clouds.

"No major convective or thunderstorm activity at the time," she said.

The South China Sea is a tense region with competing territorial claims that have led to several low-level conflicts, particularly between China and the Philippines. That antipathy briefly faded as nations of the region rushed to aid in the search, with China dispatching two maritime rescue ships and the Philippines deploying three air force planes and three navy patrol ships to help.

"In times of emergencies like this, we have to show unity of efforts that transcends boundaries and issues," said Lt. Gen. Roy Deveraturda, commander of the Philippine military's Western Command.

Malaysian missing plane map

The Beijing-bound plane went missing less than an hour after it took off from Kuala Lumpur. (CBC)

Thanh said Malaysian, Singaporean and Vietnamese search officials were coordinating operations. He said Vietnam had sent aircraft and ships scour 11,200-square-kilometer area where the plane was last known to be. Vietnamese fishermen in the area have been asked to report any suspected sign of the missing plane.

Asked whether terrorism was suspected, Malaysian Transport Minister Hishammuddin Hussein said authorities had "no information but we are looking at all possibilities."

The plane was carrying 227 passengers, including two infants, and 12 crew members, the airline said, adding that the passengers are of 14 different nationalities. All crew on board are Malaysians.

It said there were 153 passengers from China/Taiwan, 38 from Malaysia, seven from Indonesia, six from Australia, five from India, three from the U.S., two from Canada and others from France, New Zealand, Ukraine, Russia, Italy, the Netherlands and Austria.

There is no immediate information on the identities of the two Canadians on board.

In Kuala Lumpur, family members gathered at the airport but were kept away from reporters.

"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. "Our thoughts and prayers are with all affected passengers and crew and their family members."

Fuad Sharuji, Malaysian Airlines' vice president of operations control, told CNN that the plane was flying at an altitude of 10,670 metres and that the pilots had reported no problem with the aircraft.

With files from CBC News