TOKYO: Crews at Tokyo's Haneda Airport began clearing the charred wreck of a Japan Airlines plane from a runway on Friday, as investigators sought to retrieve the aircraft's cockpit voice recorder and discover what caused the deadly accident.

The Japan Airlines (JAL) passenger jet collided with a Coast Guard turboprop on the runway while landing in Tokyo on Tuesday. All 379 people on the JAL aircraft escaped before it was engulfed in flames, but five of the six crew on the Coast Guard craft died.

Two excavators equipped with cutting equipment ripped off the Airbus's wing, while another lifted debris from inside the burnt out cabin into a large lorry as around a dozen personnel in white overalls and hard hats watched on.

An official from the Japan Transport Safety Board (JTSB) said the plane's flight data recorder had been collected earlier this week but that the cockpit voice recorder had still not been retrieved.

Officials aim to complete the removal of the wreckage by Jan. 7 and it will be taken to its hangar, where the aircraft will be inspected by the Tokyo Metropolitan Police Department, broadcaster TBS reported.

Transport authorities are probing the circumstances that led to the Coast Guard plane entering the runway where the passenger jet was landing while, according to media reports, police are looking into possible professional negligence.

The captain of the Coast Guard aircraft, the sole survivor, is under scrutiny after authorities released control tower transcripts appearing to show he was ordered to enter a holding area near the runway before the crash occurred.

He said he had permission to enter the runway, the Coast Guard said on Wednesday, acknowledging there was no indication of that in the transcripts.

The captain suffered severe burns as a result of the crash and could not be reached for comment.

EMERGENCY TRIP

The Coast Guard plane was making its third emergency trip to an earthquake zone within 24 hours when the collision occurred. On the day of the accident, Haneda, the world's third busiest airport, was at full capacity, authorities have said.

Authorities have only just begun their investigations and aviation experts say it usually takes the failure of multiple safety guardrails for an airplane accident to happen.

The Coast Guard plane was on the runway for 40 seconds before the crash, local news outlets reported.

A Civil Aviation Bureau official said they were aware of the reports but hadn't confirmed it. "We are checking it currently," the official said.

U.S. aviation safety officials will provide assistance to Japan in the reading of airplane recorders to get a clearer idea of what caused the deadly collision, according to the head of the main U.S. transport regulator.

The collision marked the first time a modern lightweight airliner has burnt down and is being seen as a test case for how well a new generation of carbon-composite airplanes copes with a catastrophic fire.