One person was killed and more than 50 were injured in a blast on Wednesday at the site of an optics and optical electronics factory in the town of Sergiev Posad, 50 km northeast of Moscow, local authorities said.
Emergency services said the explosion occurred in a warehouse containing pyrotechnic equipment, state news agency TASS reported.
Andrei Vorobyov, governor of the Moscow region, said the premises had been rented by a private firm, and that a criminal investigation had been opened into possible violations of safety procedures.
He said 38 apartment blocks in the surrounding area had been damaged, along with two schools, a sports complex and a store.
TASS quoted emergency services as dismissing early reports that the blast could have been caused by a drone attack, many of which have taken place in Moscow and the surrounding area in recent weeks and months, attributed by Russia to Ukraine.
Vorobyov said 30 people had been admitted to hospital, including six in intensive care, and 26 others had been treated for lesser injuries.
Footage posted on social media, whose location and date were verified by Reuters, showed a huge column of smoke rising above the town.
The Zagorsk Optical and Mechanical Plant produces optical equipment for industrial and healthcare applications as well as for the Russian security forces.
TASS reported that a major rescue operation involving more than 150 people was underway, citing the Emergencies Ministry as saying it had sent its lead units, "Tsentrospas" and "Leader," to the site of the blast.
Russian agencies quoted local authorities as saying a state of emergency had been declared in the area.
