Seven people, including foreign nationals, were killed, and more than a dozen wounded in another blast in Iran, this time at a steel plant.

It is not known if the factory has any connection with Iran’s nuclear facilities, but Iran recently imported special steel from North Korea, possibly for use in missile engines or enrichment of uranium, a key ingredient for a nuclear weapon. The “foreign nationals” killed in the blast may have been from North Korea.

The explosion occurred Monday evening in the city of Yazd and comes after two previous blasts in the area of nuclear facilities. Yazd is located approximately 175 miles southeast of Isfahan, where an explosion severely damaged a uranium enrichment facility last month.

Iranian state television reported that five people were found dead on the scene at the steel plant and that another two died after being rushed to hospitals.

The official reason for the explosion was the presence of water in steel furnaces.