The head of the civil aviation authority in the United Arab Emirates yesterday said investigators do not believe an explosion caused the crash of a UPS cargo jet in Dubai earlier this year.

But Saif al-Suwaidi added officials were taking seriously a claim by Yemen's al- Qaeda group that it brought down the plane.

The director-general of the General Civil Aviation Authority said that while terrorism was 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 was no evidence of an onboard explosion in the 3 September 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."

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 take-off as the cockpit filled with smoke. The plane crashed into a military base after attempting an emergency landing.