The accident took place in northeast Iran on Wednesday when train wagons, packed with a cocktail of sulphur, petrol and fertiliser, derailed and blew up while they were surrounded by
firefighters and curious villagers.
"President Khatami has asked for full light to be shed on the causes of the accident," the official news agency IRNA reported.
The agency said the president had expressed his condolences to relatives of the victims and "ordered officials to carry out a serious probe".
"I hope that with more attention and responsibility we will no longer witness such sad and unacceptable accidents," he added.
The head of disaster relief in Khorassan province, Vahid Barakchi, was quoted as saying by IRNA that five villages were destroyed.
"I hope that with more attention and responsibility, we will no longer witness such sad and unacceptable accidents"
"The level of this is massive and beyond our preliminary assessments," he said.
Neyshabour chief coroner Mehran Bakili warned: "The magnitude of the explosion means that identifying the bodies will be a very slow process."
Barakchi said the explosion happened at a time when the firefighters and the rescue workers were trying to put out the fire.
"A number of the firefighters and local villagers were killed in the explosion."
Wagons in flames
Aljazeera's correspondent reported earlier that 280 people were trapped under the rubble.
Among the casualties, most of whom were firefighters, were the governor and mayor of Neyshabour, along with other officials of Mashad city, the correspondent said.
He added that 48 of the 52 wagons of the train went up in smoke, and glass windows of houses more than 10km away were shattered.
The disaster occurred in the
northeast of Iran
The massive blast occurred at Khayyam station, near the town of Neyshabour and was heard in the provincial capital of Mashhad 75km away, IRNA said.
Local officials said the rail wagons, which were parked in a nearby station, began rolling away in the early hours of the morning.
The wagons then derailed and a fire began, drawing firefighters and curious onlookers to the scene.
When the explosion occurred, the seismological unit of Tehran University recorded an earth tremor measuring 3.6 on the Richter scale in the same area - possibly a reading sparked by the force of the blast.