>>an explosion and fire at the back of the plane>>
No indication the plane tride to abort takeoff. Possibly a generator fire, but sounds more like one of the engines had a fuel problem, which would indicate why the plane had insufficient thrust to takeoff normally.
The plane was scheduled to leave at 1:00 pm, but the pilot aborted the take off because there was something wrong with the left engine. They took the plane over to the parking area and the ground crew examined it and approved it. When the pilot tried to take off the second time, around 2:25 pm, one of the engines either burst into flames or fell off (varying eye-witness accounts). In any case, the plane had reached the speed at which the take-off couldn’t be aborted, and the pilot couldn’t get the nose up enough to take off. It slid off the runway into a field, broke up, and burst into flames at the back. This also set fire to the field and brush around the plane.
It wasn’t terrorism but probably poor maintenance. The plane was about 20 years old, and was one of several of this type owned by Spanair.