Britain's BAE Systems said on Monday it was working with authorities probing the crash of a British spy plane in Afghanistan but declined to comment on the possible cause of the incident which killed 14 crew members, Reuters reported. Saturday's crash marked the fifth for the Nimrod MR2, with two of the previous four incidents blamed on onboard fires. BAE in July was awarded a 1.1 billion-pound ($2.1 billion) contract - the latest in a series to overhaul the Royal Air Force's fleet of aging Nimrod MR2s, a heavily modified version of the De Havilland Comet airliner which entered service in 1952. "BAE Systems has offered its assistance to the Royal Air Force in supporting the investigation into this tragic event," the company said in an emailed statement. "Until that investigation is concluded, it would be inappropriate for us to comment any further," Europe's largest defence company said. UK Defence Secretary Des Browne said in a television interview that the early indications pointed to "a dreadful, tragic accident". NATO said in a statement that the British plane crashed after declaring a technical problem. British military officials were quick to deny claims by the Taliban that its forces had shot down the plane, noting the crew had time to send a distress signal before crashing. In January 2005, UK officials were similarly reluctant to acknowledge the possibility that a shoulder-mounted missile had downed a C130 Hercules transport plane in Iraq. Insurgents showed a video which they claimed showed a missile firing and the wreckage and a UK probe later concluded that the plane had been shot down, killing nine Britons and one Australian. Saturday's crash of the Nimrod marked the largest single-day loss of life for British forces since the U.S.-led invasion of Afghanistan began in November 2001. The dead included 12 Royal Air Force personnel, a Royal Marine and an army soldier. The plane was based at RAF Kinloss air force base in Scotland. The incident is expected to escalate debate over whether UK forces and equipment are being overstretched in Afghanistan. Defence analysts said it could take time for the UK to replace the lost Nimrod in Afghanistan, depending on what special refitting of the plane or crew training was required beforehand. A Ministry of Defence spokesman declined to comment on how many of the planes were deployed in Iraq, Afghanistan and nearby countries. The Nimrod can stay airborne for 10 hours with a capacity for up to 25 personnel, though it most commonly flies with a crew of 13 including pilots assessing the movements of troops, equipment and civilians in an intelligence-gathering role matched by no other UK plane. Britain retired the last of its famed 3-man Canberra tactical reconnaissance planes in June.