21.   Police in Duesseldorf said Tuesday the blast was caused by an old hand grenade that had been rebuilt, but did not identify its origin.

22.   Police said it was not clear what caused the blast.

23.   Police said it was not immediately clear whether the blast was caused by a bomb that was placed in the restaurant, or by a suicide bomber.

24.   Police said the blast was caused by a suicide bomber.

25.   Police said the blast was probably caused by a kind of plastic explosive used in several other terrorist attacks in Turkish cities.

26.   Police said they had not yet determined what caused the blast.

27.   Palestinian security officials would not say what caused the blast.

28.   Police at the scene said the blast was caused by a bomb in a car that had been parked in the street shortly before the explosion.

29.   Police believe the blast was caused by workers mistakenly drilling into a gas line.

30.   Police said the blast was caused by explosives packed into a fire extinguisher.