Ho Chi Minh City (AFP) - Vietnamese searchers on Sunday spotted possible aircraft debris after combing the sea for nearly 48 hours in search of a Malaysian passenger jet that vanished with 239 people aboard, officials said.
The discovery, which could confirm the worst fears of anguished relatives, came after Malaysia's government launched a terror probe into the Boeing 777's disappearance, investigating suspect passengers who boarded with stolen passports.
"We received information from a Vietnamese plane saying that they found two broken objects, which seem like those of an aircraft, located about 50 miles (80 kilometres) to the south-west of Tho Chu Island," said an official from Vietnam's National Committee for Search and Rescue, who did not want to be named.
The island is part of a small archipelago off the south-western tip of Vietnam, and lies northeast of Malaysia's capital Kuala Lumpur, from where Malaysia Airlines (MAS) flight MH370 left early Saturday bound for Beijing.
"As it is night they cannot fish them out for proper identification. They have located the position of the areas and flown back to land," the Vietnamese official added.
Planes and boats would be sent back to the area Monday to investigate further,he said.
Two large oil slicks which authorities suspect were caused by jet fuel were detected late Saturday further south of the island chain, and observed later by an AFP journalist aboard a Vietnamese spotter plane.
Both MAS and Malaysia's civil aviation authority, however, said they had no new information to offer after the apparent Vietnamese discovery.
Malaysian officials said earlier that MH370 may have inexplicably turned back towards Kuala Lumpur as they tried to shed light on the mystery of what may have caused a reliable aircraft model with no known safety issues to slip off the radar.
The plane, captained by a veteran MAS pilot, had relayed no indications of distress, and weather at the time was said to be stable.
- 'Puzzled' -
The United States sent the FBI to investigate, but US officials stressed there was no evidence of terrorism yet.
"There is a distinct possibility the airplane did a turn-back, deviating from the course," said Malaysia's air force chief, General Rodzali Daud, citing radar data.
But Malaysia Airlines (MAS) chief executive Ahmad Jauhari Yahya said the Boeing 777's systems would have set off alarm bells.
"When there is an air turn-back the pilot would be unable to proceed as planned," he said, adding authorities were "quite puzzled" over the situation.
A total of 40 ships and 34 aircraft from an array of Southeast Asian countries, China and the US have been involved in the search, with two Australian surveillance aircraft due to join in.
After it emerged that two people boarded the flight with stolen European passports, Malaysia's transport minister Hishammuddin Hussein said he was looking at four suspect passengers in all.
He said authorities were examining CCTV footage of the two with fake passports.
"We have managed to get visuals of them," he said, adding that Malaysia was liaising with other countries' intelligence agencies on the findings. He gave no more details.
Hishammuddin also confirmed the US Federal Bureau of Investigation (FBI) was dispatching personnel to Malaysia.
"At the same time our own intelligence has been activated, and of course, the counter-terrorism units... from all the relevant countries have been informed," he said, refusing to rule out the possibility of a hijack.
Prime Minister Najib Razak was quoted by The Star newspaper saying the government would review and enhance airport security protocols, if needed.
"If necessary, because we still do not know the cause of the incident," he was quoted as saying.
Technical advisers from Boeing and the US Federal Aviation Administration are en route to Asia to help with the probe.
- Frustration -
The flight vanished about an hour after taking off from Kuala Lumpur. A total of 153 Chinese nationals were on board, and relatives camping out at Beijing's main international airport bemoaned the lack of news Sunday.
"The airline company didn't contact me, it was a friend," a middle-aged woman surnamed Nan told reporters, holding back tears. Her brother-in-law was on the flight.
"I can't understand the airline company. They should have contacted the families first thing."
MAS insisted it was doing its best to keep relatives in China informed given the confusion over the plane's fate, and was preparing to fly some of them to Malaysia on Monday to be closer to the search-and-rescue operation.
Two European names -- Christian Kozel, an Austrian, and Luigi Maraldi of Italy -- were listed on the passenger manifest but neither man boarded the plane, officials said. Both had their passports stolen in Thailand over the past two years.
Thai police said Sunday they were investigating a possible passport racket as flight information seen by AFP gave new details about bookings made in Thailand with the two stolen European passports.
The tickets booked in Maraldi and Kozel's names were made on March 6, 2014, and issued in the Thai city of Pattaya, a popular beach resort south of Bangkok.
The e-ticket numbers for their flights are consecutive and both were paid for in Thai baht. Each ticket cost THB 20,215 (US$625).
"Kozel" was booked to travel from Kuala Lumpur to Beijing on MH370, then on to Amsterdam and Frankfurt. "Maraldi" was booked on the same flights until Amsterdam, where he was to continue to Copenhagen.
Interpol confirmed that "at least two passports" recorded in its Stolen and Lost Travel Documents database were used by passengers on board the Malaysian flight.
Q&A: What happened to Malaysia Airlines flight 370?
Kuala Lumpur (AFP) - The sudden disappearance Saturday of Malaysia Airlines flight MH370 -- with no distress call or other signs of trouble -- has ignited intense speculation over what happened to the jet and its 239 passengers.
Following are some of the scenarios being mulled over by regional authorities, investigators and industry experts.
Q: Is mechanical or structural failure likely?
Sudden, accidental structural failures leading to explosions or a sudden loss of cabin pressure are considered extremely unlikely in today's passenger aircraft.
This is especially so with the Boeing 777-200 model, which has one of the best safety records of any jet.
"From a crack, there can be a whole structure breakdown that allows for no response. But in the last two to three decades there have been next to nil such incidents," said Ravi Madavaram, an aviation analyst with Frost & Sullivan.
Indonesia-based aviation analyst Gerry Soejatman said based on the MH370 plane's maintenance records, "there is nothing that would jump straight out of the page".
Q: How likely is human error in this case?
The MH370 case may draw comparisons with the crash in 2009 of an Air France into the Atlantic Ocean, which killed more than 200 people.
An investigation said speed sensors failed, causing the Airbus jet to stall and lose altitude. But it also said pilots failed to react correctly, losing control of the jet.
Soejatman said despite all the safety features on modern aircraft, well-trained pilots taking proper action in an emergency also is essential.
"If the crew is not on the ball, they quickly lose control of the situation," he said.
Q: Was it an attempted hijacking or terror attack?
This spectre has loomed after authorities said at least two passengers had boarded with stolen passports. Malaysian officials also said Sunday radar data indicated the pilot may have inexplicably tried to turn back to Kuala Lumpur.
Analysts said the absence of any distress signal raises eyebrows, as it could indicate an event so sudden that the crew could not respond.
"There was not even time for the pilot or crew to raise an alarm. It could have happened due to a deliberate act -- by a pilot or a terrorist -- but this is all very speculative," Ravi said.
The terror theory's credibility is hurt by the fact that -- so far -- no claim of responsiblity has surfaced.
"What's the motive? If they didn't bring any weapons, it is extremely difficult to get into the cockpit," said Shukor Yusof, aviation analyst with Standard & Poor's.
He also noted that stolen passports do not necessarily equate to terrorism.
Large numbers of illegal workers, as well as criminal syndicates, are known to move between Malaysia and neighbouring countries such as Thailand. The two suspect passports were reportedly stolen in Thailand.
Q: Is lax security at Kuala Lumpur International Airport (KLIA) to blame?
The modern facility does not have a history of known security breaches.
But Rohan Gunaratna, a terrorism expert at Singapore's Nanyang Technological University, said the passport issue could indicate a "glaring flaw" in the airport's immigration clearance.
He noted that Interpol maintains a database of stolen passports that should have raised red flags at the immigration counter.
"There are two categories of people who use these (stolen passports) -- criminals and terrorists," he said.
However, Shukor said the sheer volume of travellers moving through airports likely means not all forgeries can be caught.
"To blame Malaysian authorities for this is probably unfair -- they have to get it right all the time and potential hijackers just have to get through once," he said.
Q: Could violent turbulence or bad weather have brought down the plane?
This possibility is being widely discounted as all indications are that the weather was fine in the area where contact with MH370 was lost.
Q: Could it have run out of fuel?
Malaysia Airlines has said the plane was fuelled for at least eight hours of flight. The Kuala Lumpur-Beijing route lasts six hours.
Aircraft typically carry two hours' worth of fuel on top of what is needed.
Adds Ravi: "If there was a fuel loss, the pilot would have enough time to call for distress signal, and to turn around and glide back to land."