BEIJING -- Forty ships and more than 20 airplanes were searching for a missing Malaysia Airlines jet Sunday but by nightfall had not found any wreckage, Malaysian authorities said.
However, the agency said no checks of those passport numbers were made by any country between the time they were entered into Interpol's database and the time that Flight MH370 departed Kuala Lumpur early Saturday.
"Whilst it is too soon to speculate about any connection between these stolen passports and the missing plane, it is clearly of great concern that any passenger was able to board an international flight using a stolen passport listed in Interpol's databases," the agency's secretary-general, Ronald K. Noble, said in a statement.
“What is important at the moment is to find out what caused Malaysian Airways Flight 370 to go missing, and in this regard Interpol is making all needed resources available to help relevant authorities in Malaysia and elsewhere find out what happened,” he said, adding that the agency was in contact with officials in Malaysia and elsewhere to “determine the true identities of the passengers who used these stolen passports.”
A patrol ship from the Malaysian Maritime Enforcement Agency discovered a large oil slick in the waters 100 nautical miles from the city of Tok Bali on Sunday, the agency's director-general said at a press conference.
Mohd Amdan Kurish said the ship was ordered to collect samples of the oil to determine if it came from the plane, which vanished Saturday en route from Kuala Lumpur to Beijing with 239 people aboard, Malaysia's state-run Bernama news agency reported.
If the plane did crash into the sea, "obviously we will find clothes, bags and debris that float," he added. Fishermen working in the area were also going to be interviewed by the agency as part of the search operation.
Earlier Sunday, Vietnamese media reported that a Singaporean search plane had spotted “strange objects” in the waters off southern Vietnam but boats that reached the area later said the items were not from the
Indonesia, Thailand, Australia, China, the U.S. and other countries were participating in the quest to find the jetliner off southern Vietnam where the Gulf of Thailand meets the South China Sea. Malaysia was deploying submarine rescue vessels, officials said.
With no wreckage yet to examine, investigators were probing the identities of the passengers who used the stolen passports. Malaysia's acting transportation minister, Hishammuddin Hussein, said at one point Sunday that authorities were looking at four passengers "said to have been traveling on fake passports." But he later backtracked and said investigators were only looking at two suspected cases of stolen identity, creating some confusion.
Azharuddin Abdul Rahman, Malaysia's director-general of civil aviation, said at a news conference in Malaysia that investigators had closed-circuit TV images of the two men traveling on the European passports. But when journalists pressed him to describe the men physically, he declined.
"Our main concern is to find the aircraft," he said.
China's ambassador to Malaysia, Huang Huikang, said the embassy was investigating whether the two men had proper documents to go to Beijing, state-run CCTV reported.
Hugh Dunleavy, head of Malaysia Airlines' commercial operations, told reporters in Beijing: "As far as we are aware, every one of these people onboard that aircraft had a visa to go to China. Which means those passports were in possession of the Chinese Embassy before those visas were issued."
However, Beijing has a policy whereby some passengers in transit to third countries can stay in the Chinese capital for 72 hours without a visa, so the two men may have not needed to apply for a Chinese visa if they had tickets to another destination.
London's Telegraph newspaper said it had confirmed with two ticketing agents for China Southern Airlines -- which had a code-share arrangement with Malaysia Airlines for the flight -- that the two men were booked to fly on to Amsterdam on the airline KLM Saturday morning. The paper said the two tickets were numbered consecutively, suggesting that they were bought at the same time.
A travel agent in Beijing, who asked not to be identified, said airlines "have no legal means or responsibility to verify the accuracy of passport information," and that it's up to airport and immigration authorities to check documents.
"In China, it's usually very strict at the airport even for domestic travelers. Sometimes if we spell on character wrong in the customer's name, he may have a problem boarding the flight."
Noble, the Interpol chief, lamented the fact that few countries have been availing themselves of the opportunity to check passports against the agency's database. He said that last year, passengers were allowed to board planes more than a billion times without having their passports screened against the agency's database.
The United States, Britain and the United Arab Emirates are regular users of the database, he noted, with U.S. officials searching it 250 million times a year. Britain uses it 120 million times per year and the Emirates more than 50 million times annually, he said.
As the search for the aircraft continued, the head of Malaysia's air force told a news conference that military radar indicated that the jet may have turned back from its planned route.
But Rodzali Daud gave no further details, adding only that investigators "were trying to make sense" of the information.
Ahmad Jauhari Yahya, the airline's chief executive, said that if planes veer from their flight plan, they are supposed to inform air traffic control, but that no distress call or signal was received from the missing aircraft.
More than half of the passengers aboard the flight were mainland Chinese, and Malaysia Airlines said it would fly some family members from Beijing to Kuala Lumpur as early as Monday to await word on their relatives' fate. The airline was working with Chinese and Malaysian officials to get some of the next-of-kin passports and visas.
"Together with all those affected by the MH370 incident, we understand the need to provide regular updates on the progress of the search and rescue operations," Yahya said. "As the hours turn into days, we at Malaysia Airlines are similarly anxious and we appreciate the patience, support and prayers from everyone."