KUALA LUMPUR, Malaysia -- Vietnamese aircraft spotted what they suspected was one of the doors of a missing Boeing 777 jetliner Sunday, while questions emerged about how two passengers managed to board the ill-fated aircraft using stolen passports.
Interpol confirmed that it knew about the stolen passports but said no authorities checked its vast databases on stolen documents before the Malaysia Airlines flight departed Saturday from Kuala Lumpur en route to Beijing with 239 people on board.
Warning that "only a handful of countries" routinely make such checks, Interpol secretary general Ronald Noble chided authorities for "waiting for a tragedy to put prudent security measures in place at borders and boarding gates."
More than two days after Flight MH370 went missing, the final minutes before its disappearance remained a mystery. The plane lost contact with ground controllers somewhere between Malaysia and Vietnam.
However, searchers in a low-flying plane spotted an object in the Gulf of Thailand that appeared to be one of the plane's doors, the state-run Thanh Nien newspaper said.
Two ships from the maritime police were headed to the site about 60 miles south of Tho Chu island, the same area where oil slicks were spotted Saturday.
The jetliner apparently fell from the sky at cruising altitude of 35,000 miles in fine weather, and the pilots were either unable or had no time to send a distress signal -- unusual circumstances under which a modern jetliner operated by a professional airline would crash.
Authorities were checking on the identities of the two passengers who boarded the plane with stolen passports. On Saturday, the foreign ministries in Italy and Austria said the names of two citizens listed on the flight's manifest matched the names on two passports reported stolen in Thailand.
"I can confirm that we have the visuals of these two people on CCTV," Malaysian Transport Minister Hishammuddin Hussein said at a news conference late Sunday, adding that the footage was being examined. "We have intelligence agencies, both local and international, on board."
The thefts of the two passports -- one belonging to Christian Kozel of Austria and the other to Luigi Maraldi of Italy -- were entered into Interpol's database after they were stolen in Thailand in 2012 and last year, the police body said.
Electronic booking records show that one-way tickets with those names were issued Thursday from a travel agency in the beach resort of Pattaya in eastern Thailand. A person who answered the phone at the agency said she could not comment.
But no authorities in Malaysia or elsewhere checked the passports against the database of 40 million stolen or lost travel documents before the Malaysian Airlines plane took off.
In a forceful statement, the Interpol chief said he hoped "that governments and airlines worldwide will learn from the tragedy."
"Now, we have a real case where the world is speculating whether the stolen passport holders were terrorists," Mr. Noble said. "Interpol is asking why only a handful of countries worldwide are taking care to make sure that persons possessing stolen passports are not boarding international flights."
Details also emerged Sunday about the itineraries of the two passengers traveling on the stolen passports.
A telephone operator on a China-based KLM hotline confirmed Sunday that passengers named Maraldi and Kozel had been booked on one-way tickets on the same KLM flight, flying from Beijing to Amsterdam on Saturday. The passenger using the name Maraldi was to fly on to Copenhagen, Denmark, and the one using the name Kozel to Frankfurt, Germany.
She said the pair booked the tickets through China Southern Airlines, but she had no information on where they bought them.
As holders of EU passports with onward flights to Europe, the passengers would not have needed visas for China.
Malaysia's air force chief, Rodzali Daud, said radar indicated that before it disappeared, the plane may have turned back, but there were no further details on which direction it went or how far it veered off course.
Of the 227 passengers and 12 crew members on board, two-thirds were Chinese, while the rest were from elsewhere in Asia, Europe and North America, including three Americans.