DUBAI - THE head of the United Arab Emirates' civil aviation authority said on Saturday investigators do not believe an explosion caused the September crash of a UPS cargo jet in Dubai but are taking seriously a claim by Yemen's Al-Qaeda group that it brought down the plane.

Saif al-Suwaidi, director general of the General Civil Aviation Authority, told The Associated Press that while terrorism is not believed to be behind the crash, authorities are looking at all possible causes.

Asked if that included the possibility of a bomb that failed to detonate properly or another device sent to deliberately cause damage, al-Suwaidi said: 'Everything is possible. We are revisiting everything.' He reiterated that there is no evidence of an onboard explosion in the Sept 3 crash, which killed the two pilots.

'A terror act is an unlikely cause. But it doesn't mean we eliminate it,' he said. 'The investigation is ongoing. Of course we are investigating all possibilities.' Yemen's Al-Qaeda in the Arabian Peninsula claimed responsibility on Friday for the crash of the UPS cargo plane and last week's international mail bomb plot.

In the September crash, a fire onboard the three-year-old Boeing 747-400 cargo plane prompted the pilots to turn back to Dubai shortly after takeoff as the cockpit filled with smoke.

The cause of the fire is unknown. The plane crashed into a military base after attempting to make an emergency landing. Crash investigators have found no evidence of an explosion on board, saying there was no recorded change in pressure or other information on data recorders to indicate a blast. An official familiar with the investigation in the US has also said there is no sign the crash was caused by a bomb.

UAE takes Qaeda claim seriously