The explosion happened on Wednesday morning at around 10:40 a.m. local time at a pyrotechnics warehouse, which was being rented out on the optical-mechanical plant's territory by a private company, the Moscow Region Governor Andrei Vorobiev said.
Among the injured, five are currently in critical condition, according to preliminary information provided by local authorities. Moreover, five people could still be trapped in the rubble.
Vorobiev said people have been evacuated from all the buildings and workshops of the plant, as well as from a kindergarten close to the factory.
Blast at optical equipment plant rocks Sergiev Posad near #Moscow
A total evacuation has been declared at the plant, the city authorities said.
The Moscow Region Governor also mentioned that a sport complex near the plant had been damaged, as well as windows in nearby residential buildings.
"The Mash Telegram channel shared footage from a nearby security camera that captured the moment of the explosion, showing a fireball and a plume of smoke rising in the distance. It claimed, citing eyewitnesses, that the blast shattered windows in at least ten nearby buildings, with ceilings collapsing in offices close by," Russia Today reported.
Local media, citing a State Duma deputy, suggested that the blast could have occurred due to a "violation of technological processes." In response, Russia's Investigative Committee has initiated a criminal case into the incident.