The warehouse is privately rented from a factory that makes medical equipment and optical equipment for Russia's security forces.
At least 31 people were injured after a warehouse containing pyrotechnics exploded at a factory north of Moscow, the governor of the Moscow region, Andrei Vorobyov, said Wednesday.
Russian social media channels shared footage which showed huge plumes of smoke billowing into the air and shattered windows.
According to the governor, 19 people were taken to the hospital, three were moved to intensive care units with serious injuries.
Vorobyov said glass windows had been blown out in nearby residential flats and that the surrounding area has been evacuated.
The governor said on his Telegram channel the explosion had taken place in a 40 square metre privately rented from the factory.
The Zagorsk factory website says the plant makes medical equipment, but also optical equipment for Russia's security forces.
Sergiev Posad is part of a group of towns known for their ancient Russian churches and is a Russian tourist attraction.