Neyshabur, Iran ? Runaway train cars carrying a lethal mix of fuel and chemicals derailed, caught fire and then exploded hours later Wednesday in northeast Iran, killing more than 200 people, injuring at least 400 and leaving dozens trapped beneath crumbled mud homes.

Many of those reported dead were firefighters and rescue workers who had extinguished most of the blaze outside Neyshabur, an ancient city of 170,000 people in a farming region 400 miles east of the capital, Tehran.

The dead also included top city officials — including Neyshabur’s governor, mayor and fire chief as well as the head of the energy department and the director-general of the provincial railways — who had all gone to the site of the derailment, the official Islamic Republic News Agency reported.

The explosion devastated five villages, where authorities rushed in blood supplies and appealed through loudspeakers for donors. Hardest hit was Hashemabad, where 41-year-old Zahra Rezaie, whose mud home was near the tracks, was cooking lunch for her family when she heard the explosion and felt the ground shake. Then the ceiling collapsed.

“It knocked down and broke some dishes. I was sure it was an earthquake, and my first thought was to rush to the school and save my children,” Rezaie told The Associated Press. Her children were safe.

An AP photographer who arrived in Dehnow, one of the severely damaged villages close to the train tracks some 500 yards from the blast, said the village’s homes were flattened.

“The houses are all built of clay, and nearly every one has been destroyed, like they had collapsed in an earthquake,” Hassan Sarbakhshian said. “Everyone appears to have been evacuated,” he said, adding he could see thick, black smoke billowing about 500 yards ahead.

Rescue workers, aided by cranes and giant floodlights, worked into the night shrouded in toxic fumes, as they searched for dozens of people thought to be trapped in their clay homes devastated by the blast.

The blast was so powerful that windows were shattered as far as six miles away. In an apparent indication of the explosion’s force, Iranian seismologists recorded a 3.6-magnitude tremor in the area, IRNA reported.