Officials in Taiwan say the jumbo jet that crashed on Saturday with 225 people on board disintegrated in mid-air before plunging into the sea.

Chief crash investigator Kay Yong said the plane - operated by the Taiwanese flag-carrier China Airlines - had broken up into four large parts.

The plane vanished from radar screens 20 minutes into a routine flight to Hong Kong.

Rough seas are hampering rescuers, who say there is little hope of finding anyone alive.

More than 80 bodies have so far been recovered.

Cause unclear

Kay Yong - managing director of Taiwan's Aviation Safety Council - said military radar provided a clear picture of the plane splitting up.

"We are quite sure now that the Boeing 747-200 suffered in-flight break-up above an altitude of 30,000 feet (9,100 meters) and broke into four large parts."

It is not clear what caused the aircraft to disintegrate in mid-air. Among the causes mentioned are internal explosion, sudden cabin de-pressurisation, a mid-air collision, or even a military accident.

China Airlines accidents

1999 - MD11 airliner crash lands in Hong Kong, killing three people 1998 - A300-600 airliner crashes near Taipei in fog and rain, killing all 197 on board and at least seven on ground 1994 - A300-600 crashes during approach in Nagoya, Japan, killing 264 people 1989 - 737-200 hits mountain near Hualien, Taiwan, killing 56 people

The government has ordered China Airlines to ground its remaining four Boeing 747-200 planes which are used for carrying cargo.

Explaining the decision, Deputy Transport Minister, Chang Chia-chu said: "There are many causes that could lead to high altitude disintegration. It might have something to do with the plane's structure and mechanical problems."

Speculation that the aircraft exploded in mid-air had been fuelled by the discovery of aircraft debris more than 70 kilometres (48 miles) away, on the west coast of Taiwan.

The search is continuing for the plane's "black box" flight recorders. Contrary to earlier reports, they have not yet been located.

Little hope

Military planes, helicopters and vessels have been scouring the crash area in the Taiwan Strait, with diminishing hopes of finding anyone alive.

The Taiwan Coast Guard is continuing its search

"There is almost no chance for survivors," said Chang Kuo-cheng, director of Taiwan's Civil Aeronautics Administration (CAA).

"Given the high altitude when it started plunging into the sea, I don't think any person could stand the impact."

Relatives of some of the victims have been flown to the scene of the disaster to help with the identification process.

Poor safety record

Many of Taiwan's Sunday newspapers carry articles attacking China Airlines for its poor safety record - Saturday's accident is its fourth major crash in less than 10 years.

The company said the Boeing 747 that crashed on Saturday was built in 1979 and was the last plane of its kind in the airline's fleet.

It was reportedly its last flight for China Airlines, as it had been sold to a Thai carrier.

The crash of Flight CI 611 follows two major accidents in the region involving mainland Chinese airlines during the past month.