US crash experts have joined the hunt for clues about what caused a Taiwanese China Airlines airplane to break apart in mid-air on Saturday, leaving all 225 people on board feared dead.

Relatives have been helping to identify bodies

Taiwanese officials said the US team was involved because of its experience with two other crashes which appear to have similarities with the China Airlines crash, and which also needed deep-sea salvage skills.

The two crashes were a mid-air explosion of a TWA Boeing jet in 1996 off the New York coast, and a SwissAir MD11 which broke up off Canada after leaving New York in 1998.

Investigators later attributed the TWA crash to an explosion in the plane's fuel tank.

Aviation specialists have put forward several theories about the causes of the China Airlines crash - an internal explosion, sudden cabin depressurisation, a mid-air collision, or a military accident.

'Black box' search

The US investigators will also help search for the Boeing 747-200's vital "black boxes" - the cockpit voice recorder and the flight data recorder - and other debris from the plane.

Signals believed to be coming from the boxes on Monday were later disregarded as false.

Naval mine hunters, divers and salvage specialists have already been combing the sea for evidence, joined by hundreds of bereaved relatives who have sailed out to offer prayers for their loved ones.

So far 88 bodies have been recovered, many of which were found with broken bones, dislocated jaws and no signs of burns, according to witnesses and officials.

Kay Yong, director of Taiwan's Aviation Safety Council (ASC), said that debris was actually more valuable than the black boxes, which might have lost all power and failed to record the moment when the plane broke apart in mid-air.

"The wreckage probably could tell more about conditions or the time of in-flight break-up, and help us look for the possible cause," he added.

Military radar has already indicated that the plane broke above an altitude of 30,000 feet (9,100 metres) into four chunks - three of which flew towards the south-west, and one in the opposite direction.

The plane, China Airlines' flight CI 611 from Taiwan to Hong Kong, disappeared from radar screens at 1528 local time (0728 GMT) Saturday, 20 minutes after it took off from Taipei's international airport.

Troubled airline

Saturday's accident was China Airlines' fourth major crash in less than 10 years. The company said the plane was built in 1979 and was the last of its kind in the airline's fleet.

China Airlines accidents

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

A lawmaker for the Taiwan opposition DPP party demanded on Tuesday that Mr Yong resign from his position as the leader of investigations into Taiwanese air accidents.

"There have been so many domestic air accidents, but they (the ASC) didn't try to find out what caused them... he (Yong) ... just does public relations."

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

The crash of China Airlines flight 611 follows two major accidents in the region involving mainland Chinese airlines in the last six weeks.