(CNN) -- Despite the efforts of 34 planes, 40 ships and search crews from 10 countries, officials have not found any sign of a Malaysia Airlines flight that went missing nearly three days ago.
"Unfortunately, ladies and gentlemen, we have not found anything that appear to be objects from the aircraft, let alone the aircraft," Azharuddin Abdul Rahman, director general of the Malaysian civil aviation department, told reporters Monday.
So the mysteries surrounding Malaysia Airlines Flight 370 -- and the true identities of some of its passengers -- remain unsolved.
Rahman discounted media reports that a plane door had been spotted.
"That report was not verified officially by the Vietnamese authorities," he said.
Another report said the plane's tail had been found. That, too, is untrue, he said.
The only lead investigators had -- an oil slick that a Vietnamese plane spotted 90 miles south of Vietnam's Tho Chu Island in the Gulf of Thailand -- turned out to be a dead end, too.
A sample from the slick showed it was bunker oil, which is typically used to power large cargo ships, and not aircraft oil, Malaysia's state new agency, Bernama, reported Monday. The agency cited the Malaysian Maritime Enforcement Agency's eastern regional enforcement chief, Datuk Nasir Adam.
No emergency signal has been detected by any search vessel or aircraft. And family members of passengers are being told to prepare for the worst.
"For the aircraft to go missing just like that ... as far as we are concerned, we are equally puzzled as well," Rahman said.
"We have to find the aircraft."
So far, nothing
Malaysia Airlines Flight 370 took off from Kuala Lumpur shortly before 1 a.m. Saturday (1 p.m. Friday ET). The Boeing 777-200ER, carrying 227 passengers and 12 crew members, went missing while flying to Beijing.
Since then, teams of searchers from Vietnam, China, Singapore, Indonesia, the United States, Thailand, Australia, the Philippines and New Zealand have been working alongside Malaysians to scour the Gulf of Thailand, part of the South China Sea that lies between several Southeast Asian countries.
The focus has now shifted to the Andaman Sea, near Thailand's border, after radar data indicated the plane may have turned around to head back to Kuala Lumpur.
But the pilot apparently gave no signal to authorities that he was turning around.
From 7 a.m. to 7 p.m., planes flew over the vast waters. Ships searched through the night.
One promising lead has turned out to be a dead end. A "strange object" spotted by a Singaporean search plane late Sunday afternoon is not debris from the missing jetliner, a U.S. official familiar with the issue told CNN on Sunday.
"We need hard evidence. We need concrete evidence," Rahman said. "We are increasing our efforts to do what we have to do."
The stolen passports
It is perplexing enough that a jetliner seemed to have vanished without a trace. Adding to the mystery is the news that at least two people on board were traveling on passports stolen from an Austrian and an Italian.
The two passengers who used the passports in question appear to have bought their tickets together.
Interpol tweeted Sunday it was examining additional "suspect #passports."
"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," said Interpol Secretary General Ronald K. Noble in a statement.
The passport mystery raised concerns about the possibility of terrorism, but officials cautioned that it was still too early to arrive at any conclusions.
One possible explanation for the use of the stolen passports is illegal immigration.
There are previous cases of illegal immigrants using fake passports to try to enter Western countries. And Southeast Asia is known to be a booming market for stolen passports.
Five passengers ended up not boarding the aircraft. Their bags were removed and were not on board the jet when it disappeared, Rahman said at Monday's briefing.
Could the plane have been hijacked? "We are looking at every angle, every aspect," Rahman said.
"We are looking at every inch of the sea."
For the relatives of the 227 passengers and 12 crew members, the wait has been agonizing.
Among the passengers, 154 people were from China or Taiwan. The plane was also carrying 38 Malaysians, five Indians and three Americans citizens. Five of the passengers were younger than 5 years old.
In Beijing, family members gathered in a conference room at a hotel complex.
More than 100 people signed a hand-written petition that demanded "truth" from the airline. They also urged the Chinese government to help them deal with Malaysian authorities.
Malaysia Airlines, which was helping family members apply for expedited passports, said it will fly out five relatives of each passenger to Kuala Lumpur.
A fuller picture of what happened may not become available until searchers find the plane and its flight data recorder.
And so far, that hasn't happened.
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