More than 200 people were feared killed when rail wagons carrying sulphur, petrol and fertiliser derailed and exploded in Iran on Wednesday.
Many more were injured in the blast, which took place near the town of Neyshabur in Khorassan province, Irna news agency reported.
BBC quoted a local official as saying that the explosion occurred when fire-fighters were trying to extinguish the blazing wagons.
Vahid Barakchi said five villages were destroyed by the blast.
"The scale of the accident is very extensive and the damage seems to be more than initial estimates suggested," he added.