The crew of an RAF reconnaissance plane reported a fire shortly before it crashed in Afghanistan with the loss of 14 lives, the force's chief has said.
A routine refuelling took place before the Nimrod crash
Twelve RAF personnel, a Royal Marine and an Army soldier were on board the Nimrod MR2 which came down on Saturday.
Chief of the Air Staff Air Chief Marshal Sir Glenn Torpy said a routine air-to-air refuelling had taken place just before a mayday call was received.
Indications are a technical problem was linked to a blaze, he told Channel 4.
"We have definitely got an early report that the pilot reported a technical problem connected with fire," he said.
The Nimrod was said to have completed routine mid-air refuelling at 20,000 ft (6,000 m).
"It was obviously carrying out a surveillance operation over Afghanistan and all the indications from the circumstances, from the information that we have at the moment, are that it was technical malfunction," the air chief marshal said.
Claims by the Taleban that they had shot the plane down have been dismissed.
Air Chief Marshal Torpy also said it was "pretty unlikely" that a Taleban missile had hit the disabled plane as it flew at low altitude.
The Nimrod was equipped with "very comprehensive" defensive facilities, he said.