At least 30 people have been killed in a series of blasts and a fire that engulfed a pharmaceutical plant in central Iran.

The incident happened yesterday when a container of chemicals caught fire at the factory near the city of Arak, 290km southwest of Tehran.

Another 38 people were injured at the factory.

A container holding 60,000 litres of inflammable products exploded during welding work nearby and the fire quickly spread to other parts of the plant.

There was extensive damage to nearby buildings with many vehicles destroyed and the roofs of buildings collapsing.

Many of the dead were burned beyond recognition and 23 of the injured suffered burns of 70% or more, the witnesses said.

Provincial officials said most of the factory had been destroyed but that the fire had been brought under control.