The mysterious disappearance of Malaysia Airlines Flight 370 remains unexplained, even though multinational search teams are in the Asian waters, where it is thought to have gone down, and in the air, searching relentlessly.

One consideration of the disappearance is foul play, as suspicions were raised by officials discovering that two passengers were traveling on fake passports. Interpol said in a statement it was investigating all other passports used to board Flight MH 370 and was working to determine the “true identities” of the passengers who used the stolen passports.

“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.”

A technical malfunction or an explosion caused by terrorism are among possibilities under scrutiny as the search for wreckage continues. Mostly due to the lack of any warning or communication from the flight deck, suggesting a sudden, catastrophic incident.

However, with technical difficulty it is unlikely that a mayday or radio contact would not have been made. At cruising altitude in good weather, even with a total loss of engines – pilots would have ample time to make an emergency call.

Because of the lack of wreckage in the areas being searched makes it more likely that the plane blew up high in the air, rather than breaking up upon sudden impact with water.

A third theory is that the plane was deliberately steered into the sea, under duress by a hijacking, or by the pilot committing suicide.

Meanwhile, Thailand’s navy is shifting its search focus away from the Gulf of Thailand and the South China Sea, Thai Navy Rear Adm. Karn Dee-ubon told CNN on Sunday. The shift came at the request of the Malaysians, who are looking into possibilities that the plane could have turned around and could have gone down in the Andaman Sea, near Thailand’s border, Karn said.

But the pilot appears to have given no signal to authorities that he was turning around, the officials said.

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.

By the end of the day Sunday, more than 40 planes and more than two dozen ships from several countries are involved in the search. And if that isn’t enough, the Chinese navy dispatched a frigate and an amphibious landing ship, according to a online post by China’s navy. Those ships are expected to arrive on site Monday morning.

Malaysian authorities have not yet confirmed the report of the oil slicks spotted from the air, which came from Vietnam’s official news agency.

But there are certainly big questions that far outweigh the few fragments of information that have emerged about the plane’s disappearance.

And lets not forget the relatives of the 227 passengers and 12 crew members on board. The agony of not knowing what really happened, and the wait for their friends and loved ones that most likely will not return.

Among the passengers, there were 154 people from China or Taiwan; 38 Malaysians, and three U.S. citizens. Five of the passengers were younger than 5 years old.

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