At least 79 people have been injured in an explosion in a plant in Russia.

The blast took place on Saturday at the Kristall explosives factory in Dzerzhinsk, 250 miles (400km) east of Moscow. The cause has not been determined.

The Russian health ministry said 38 employees at the plant and 41 local residents sought treatment after the blast. It said 15 were hospitalised, one in serious condition.

The blast broke windows in about 200 homes near the plant, the Interfax news agency cited regional authorities as saying.

Dmitry Krasnov, the deputy governor of Nizhny Novgorod, the region that includes Dzerzhinsk, said earlier on state TV that two people were missing in the blast, but later said that information had not been confirmed.

Representatives of Kristall told Interfax that five people were working in the area where the explosion occurred and were safely evacuated.

There was no information yet on where the injured were at the time of the blast.

“There was a technical explosion in one of the workshops, followed by a fire of around 100 sq metres,” a spokesman for the local emergency ministry said.

Images on social media showed a large cloud of smoke after the explosion.