The search for a missing Malaysia Airlines flight, carrying 239 people, continued on Saturday afternoon after it went missing earlier somewhere in the South China Sea between Malaysia and Vietnam.

Two large oil slicks, between 6 and 9 miles long, spotted by a Vietnam Navy aircraft in an area where the Boeing 777 is thought to have disappeared may be one of the first signs that the plane crashed, although nothing has been confirmed.

The Vietnamese government says that the oil spill, spotted near the southern tip of Vietnam, could be from the jet engines of the missing plane.

Vietnamese Navy aircraft captured late Saturday an aerial view of oil on the surface of the water near the southern tip of Vietnam that could be a sign of the missing plane. REUTERS/Trung Hieu/Thanh Nien Newspaper

“We have announced that information to Singapore and Malaysia and we continue the search," Lai Xuan Thanh, the director of the Civil Aviation Administration of Vietnam told The New York Times.

The Vietnamese government said it was sending vessels to investigate the oil slicks, which can be seen about 90 miles south of Tho Chu island. Malaysia, Singapore, China, and the Philippines have also contributed planes and ships to the search effort. The U.S. Navy said it was sending a nearby destroyer to the region.

Malaysia Airlines Flight 370 has been missing since early Saturday morning. Flight MH370 was flying from Malaysia's capital, Kuala Lumpur, to Beijing, a route that normally takes six hours. The flight left from Kuala Lumpur at 12:41 a.m. local time and was expected to land in Beijing at 6:30 a.m. According to the airline, the aircraft fell off the radar at 2:40 a.m., around two hours after departure.

The missing plane did not send a distress call and at takeoff had enough fuel to fly for seven hours. Thanh told The Wall Street Journal, that there were no reports of bad weather along the flight's route.

The aircraft was carrying 227 passengers, who hailed from 14 different countries, and 12 crew members, all from Malaysia. Two infants and three young children were among the passengers. The majority of passengers were Chinese, Xinhua reports. The U.S. state department said that there were three Americans on board.

Family members of those onboard the missing Malaysia Airlines flight MH370 are interviewed by media at the waiting area at Kuala Lumpur International Airport in Sepang March 8, 2014. REUTERS/Samsul Said

In a strange development, officials said two of the passengers listed on the manifest were not on board and had had their passports stolen. The Rome Foreign Ministry said that Luigi Maraldi, an Italian man, reportedly had his passport stolen last year in Thailand. Similarly, an Austrian Foreign Ministry spokesman told Reuters that an Austrian citizen listen on the manifest was not on board and had his passport stolen in Thailand two years ago.

“While the stolen passports are interesting, they don’t necessarily say to us that this was a terrorism act," a senior U.S intelligence official told The New York Times.

The captain and first officer of the plane were experienced pilots. Capt. Zaharie Ahmad Shah, 53, began with the airline in 1981 and had logged 18,365 flying hours, while First Officer Fariq Ab.Hamid, 27, joined in 2007 and had 2,763 hours logged.

The search continues

"At the moment we have no idea where this aircraft is right now," Malaysia Airlines Vice President of Operations Control Fuad Sharuji said earlier on CNN's "AC360."

Officials said that the plane was last detected in a region where the South China Sea meets the Gulf of Thailand, according to the AP.

Fortunately, the Gulf of Thailand is just 250 feet deep at its deepest point, according to airline analyst Robert W. Mann, Jr., which would aid in search and rescue efforts.

Although the sea search will continue overnight, the air search will resume in the morning.

The Boeing 777 flown by Malaysia Airlines is known as one of the world's safest jets. The only fatal accident in the aircraft's 20-year-history happened last July when an Asiana Boeing 777 crashed at San Francisco International Airport.

Malaysia Airlines also has a good safety record. The last fatal accident was in 1995.

"We are doing everything in our power to locate the plane,"a Malaysian Airways official told Reuters. "We are doing everything we can to ensure every possible angle has been addressed. We are looking for accurate information from the Malaysian military. They are waiting for information from the Vietnamese side."

Boeing tweeted this statement: "We’re closely monitoring reports on Malaysia flight MH370. Our thoughts are with everyone on board."