Seven people were killed by an explosion in a steel plant in the central province of Yazd on Sunday night, the semi-official Mehr news agency reported Monday.

The incident took place at the privately owned Ghadir steel plant which is located in the city of Ardakan, the report said.

Some of the people killed in the incident have foreign nationality, according to the report. Twelve people were also injured in the explosion.

The cause of the incident has not been revealed yet and investigations are underway.