DUBAI, United Arab Emirates -- The head of the United Arab Emirates' civil aviation authority said 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 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 U.S. has also said there is no sign the crash was caused by a bomb.
The probe has been focused on determining whether the fire was caused by a technical malfunction or flammable cargo such as lithium batteries that power electronic gadgets such as cameras, cell phones and laptop computers.
The Emirates is leading the probe with help from the U.S. and the plane's manufacturer, Boeing Co.
One of two packages in last week's mail bomb plot was discovered by UAE authorities in Dubai.
Officials late Thursday said they were tightening security at airports across the seven-state UAE federation to more closely monitor goods from certain countries.
Al-Suwaidi would not provide details of the new measures. But he defended the country's aviation security as "the highest maybe in the world," and said it was sufficient to keep travelers and crew safe.
"We are conscious not only for Yemen, but other countries also. We are concentrating on having a system in place to prevent penetration from any part of the world," he said.