U.S. officials are working to find out as much as possible about two apparently stolen passports connected with the missing Malaysia Airlines jet that vanished this morning near Vietnam.
Confirmation of the safety of two passengers, one Italian and one Austrian national, whose names appeared on the plane's passenger manifest but were not in fact on board the flight, has added to the mystery surrounding missing Malaysia Airlines Flight MH370, which was carrying 239 people.
The fact that there were apparently two males on board the flight posing as an Austrian and an Italian is tantalizing and suspicious, and could be meaningful, or it could have nothing at all to do with what happened to the plane, sources said.
An Austrian Foreign Ministry press spokesperson confirmed via Twitter today that the Austrian passenger supposedly on the flight was in fact "safe and sound in Austria," and had his passport stolen in 2012.
Meanwhile, an Italian Foreign Ministry press office official told ABC News that no Italian was on the plane. The parents of Italian Luigi Maraldi, whose name is also on the passenger manifest, told Italian TV station RAI that their son had called them early this morning from Thailand where he is vacationing. Maraldi's passport was stolen about a year ago while he was on vacation in Thailand, his parents said.
Official sources told ABC News today they are investigating the two stolen passports and hoping that the Malaysian airport has security cameras that recorded passengers headed to the flight. Those images can be compared to various databases, provided they exist and the Malaysians will share them.
The U.S. government is also planning to review all the names of passengers and crew on the flight manifest, sources said. The names, which are available through open source, will be run through all relevant terrorism and criminal databases the government has access to. A formal request may have already been made through the TSA or State Department, one official said.
U.S. officials emphasized that there is no evidence of terrorism, but it is conducting the review to check for any potential leads. They are not ruling anything out at this stage, especially considering so few facts have been revealed in the case and no wreckage has been recovered, sources said.
Authorities volunteered tonight that stolen passports and counterfeit passports are often used for drug smuggling in that area of the world.
Meanwhile, a massive search and rescue operation is currently under way for the Boeing 777-200 aircraft, more than 24 hours after air traffic controllers lost contact with the plane.
A spokesman for Malaysia Airlines said Friday that the passengers included travelers from America, Canada, Britain, Australia, France, India, the Netherlands, Russia and several other countries.
"An international search and rescue mission from Malaysia, Singapore and Vietnam was mobilized this morning. At this stage, they have failed to find evidence of any wreckage. The sea mission will continue overnight while the air mission will recommence at daylight," Malaysia Airlines said in a statement posted on its website at 2 a.m. local time Sunday.
The three Americans on board the Malaysia Airlines flight that went missing in Southeast Asia have been identified as Philip Wood, 51; Nicolechd Meng, 4; and Yan Zhang, 2, according to the flight's manifest.
The Vietnamese government reported today that air force pilots spotted large oil slicks off the country's southern coast, according to The Associated Press. There was no confirmation that the slicks were related to the missing plane, but the statement said the slicks were consistent with the kinds expected to be left by a crashed jetliner.
China has dispatched two maritime rescue ships and the Philippines deployed three air force planes and three navy patrol ships to help. The Navy's USS Pinckney is also on its way to help the search effort, the 7th Fleet announced on Twitter this morning.
Flight MH370 departed Kuala Lumpur at 12:55 a.m. local time Saturday, and was scheduled to land in Beijing at 6:30 a.m., the airline said. It went missing two hours into the flight and disappeared off the radar.
The plane's route would take the aircraft from Malaysia across to Vietnam and China. Vietnam said on its official website that its air traffic controllers lost contact with the plane "in Ca Mau province airspace before it had entered contact with Ho Chi Minh City air traffic control." Ca Mau is near the southern tip of Vietnam.
The plane was meant to transfer to Ho Chi Minh City air traffic control at 1722 GMT but never appeared, the statement said, citing a senior Ministry of Defense official.
Malaysia's defense minister told a news conference, "We are trying to do everything in our power to [determine] where the plane is."
Malaysia Airlines said the captain of the airliner, Zaharie Ahmad Shah, was an experienced 53-year-old pilot who had 18,365 hours of flying since joining the airline in 1981. The first officer on the flight was identified as Fariq Hamid, 27, and had about 2,800 flight hours since 2007.
Meanwhile, the flight information board at the airport in Beijing indicated the flight was delayed.
An airport official wrote on a white board near the arrivals customer service desk that families of the missing passengers should go to the Lido Hotel. The notice was put up about four hours after the plane was overdue.
"Friends and families should go to the Lido Hotel for more information," Eric Yangchao, customer service representative for Beijing International Airport, told ABC News. Family members took a shuttle bus to the hotel.
In a statement on Twitter, Boeing said it was watching the situation closely. The Malaysian aircraft, a Boeing 777-200, is 11 years and 10 months old. The 777 model had not had a fatal crash in its 20-year history until the Asiana crash in San Francisco in July 2013.
ABC News' and Joohee Cho contributed to this report.