By Michael Bristow in Taiwan

Although investigators have yet to examine all the evidence relating to the China Airlines plane which plunged into the sea off Taiwan, that has not stopped speculation as to the cause of the tragedy.

Crash theories, which are being put forward by pilots, aviation experts and even ordinary people, range from the credible to the highly unlikely, such as a meteor strike.

Maybe there was a bomb or a dangerous substance on board which exploded, but then why aren't the bodies burned?

Taipei student Wang Pei-chun

The plane's sudden disappearance from radar screens about 20 minutes after take-off on Saturday on a flight from Taipei to Hong Kong has led many to suggest the plane suffered a mid-air explosion.

But officials from Taiwan's Aviation Safety Council (ASC), which is investigating the crash with experts from the US National Transportation Safety Board and the Boeing company, are refusing to be drawn into the speculation.

All they have said is that they believe the plane, which had 225 people on board, broke up above an altitude of 30,000 feet (9,100 metres), with pieces flying off in four separate directions.

Fuel-tank explosion?

Despite the ASC's reticence, others are offering their theories.

An un-named Taiwanese pilot was reported in one newspaper as saying: "Talking to several other pilots after we heard about the crash, we all agreed it suffered the same fate as TWA Flight 800 - a centre fuel-tank explosion."

The Taiwan Coast Guard is continuing its search

Although he did not want to speculate on the cause of this particular crash, Phil Tai, a safety investigator with the ASC, said there were a number of credible possibilities as to why a plane might suddenly break up in mid-air.

He said metal fatigue was one possibility, although a China Airlines spokesman said the 23-year-old aircraft which crashed off the Penghu island chain on Saturday had undergone a thorough structural check-up last November.

Another possibility is that extremely high cabin pressure could have caused the plane to disintegrate, but the safety investigator said this only happened "very rarely".

Flying the plane faster than it should be flown could also force the plane to break up, according to Mr Tai, as could a collision with an "external force".

He added: "A very severe, high level of turbulence might also cause this effect, as could, of course, some kind of explosion on the plane itself."

Missile theory

Tai said there was only a "very, very remote" chance a meteor could have hit the plane.

Investigators are desperately looking for clues

Another popular theory, which was quickly dismissed by Taiwanese military and government officials, was that a stray missile, from either Taiwan or China, caused the explosion.

Taipei student Wang Pei-chun said she also thought this unlikely:

"Maybe there was a bomb or a dangerous substance on board which exploded, but then why aren't the bodies burned?

"China wouldn't fire a missile at a plane, there's no reason to do this. And safety checks would have been carried out before the plane took off so I don't think it's anything to do with the plane's age," she added.

The crash has not put the 25-year-old off flying China Airlines. "It's notorious for accidents but accidents are rare. I won't stop using them. And now their tickets will probably be cheaper."

Fearful

But it would discourage Chuang Xiou-mei, a 40-year-old restaurant owner, from taking to the skies.

"I was thinking of going to China later this year, but now I don't think I'll bother," she said.

Whatever the cause of the crash, the incident has left many Taiwanese shocked and eager for answers.

Professor Sun Chung-hsing, a sociologist at National Taiwan University, said: "I think people in Taiwan believe more and more that we are doomed.

"We have one accident after another, earthquakes, the unemployment rate is getting higher, and we still have water shortages. People feel powerless and helpless."