MOSCOW: Forty-three people have been injured so far in a blast at an optical-mechanical plant in the city of Sergiev Posad in the Moscow region, local authorities said.

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, said Governor of the Moscow Region Andrei Vorobiev in a Telegram post.

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, Xinhua news agency reported.

He also added that a sport complex near the plant had been damaged, as well as windows in nearby residential buildings.

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.