While Teksler did not specify which facility was affected, verified footage shows a massive fireball near the Plastmass plant, which manufactures and recycles explosives for Russia’s military.

Authorities have yet to determine the cause of the explosion, but the governor emphasized that it “was not a drone attack.”

The fire, first reported late Wednesday, has since been extinguished, though search and rescue operations continued Thursday morning. Ten workers remained unaccounted for, Teksler said.

Friday has been declared a regional day of mourning, and investigators have launched a criminal probe into the incident.

BBC Verify confirmed two videos of the explosion—one from CCTV roughly 3km (1.9 miles) away capturing the moment of the blast, and another showing the fireball from a passing vehicle on a nearby road.