By Dasha Litvinova and Emma Burrows

TALLINN, ESTONIA — An explosion on the grounds of a factory that makes optical equipment for Russia’s security forces injured 56 people Wednesday north of Mos- cow, six of them severely, officials said.

The blast occurred at a warehouse storing fireworks but was on the grounds of the Zagorsk optics man- ufacturing plant, Andrei Vorobyov, the governor of the region surrounding the Russian capital, said. The explosion damaged 38 apartment buildings and prompted an evacuation of the surrounding area, the regional governor said. Five people were feared trapped under rubble.

Vorobyov said the com- pany rented out the ware- house for storage, but he later claimed the plant itself was mostly producing pyro- technics. He said the Zag- orsk Optical-mechanical Plant “has had nothing to do with optics or mechan- ics for a long time.”

The company’s website says it still manufactures those products, as well as medical equipment. A 1995 report by the U.S. Department of Commerce described the factory as “a producer of precision opti- cal equipment for the mil- itary.”

Russian investigative news outlet Agentstvo reported Wednesday that state procurement data from recent years showed the plant supplied binoculars and dosimeters to Russia’s National Guard, produced equipment for military aircraft and was involved in the development of a new fighter-bomber.

Russian authorities feared five people were missing in the aftermath of the explosion. Emergency crews with sniffer dogs walked over the rubble of low brick buildings, video from the scene showed. Firefighters hosed down the mangled industrial wreckage.

Russian officials did not provide a suspected cause of the explosion, which produced a tall plume of black smoke and added to jitters over recent nighttime drone attacks on Moscow. Earlier, officials said Russian air defenses shot down two drones aimed at the capital overnight, and they accused Ukraine of an attempted attack.

Some Russian media reported that a drone attack caused the blast at the manufacturing plant site. Multiple Russian authorities, including Vorobyov and Russia’s Investigative Committee, denied that.