Several people were injured in an explosion at a factory in Russia's Chelyabinsk Oblast region on Thursday. 

The blast occurred at a copper smelting factory in Chelyabinsk, Russian news agency TASS reported.

At least 10 people were injured in the blast, and at least four people are said to be in a critical condition. 

The explosion was reported from one of the workshops at the copper smelting plant, which is said to be the oldest factory in the region producing blister copper. 

On Wednesday, another blast was reported at a gunpowder factory in Russia's Tambov Region, in which four people were injured, local media reported.