At least 25 people were injured in an explosion at an industrial plant northeast of Moscow, Russian state news agency RIA Novosti reported Wednesday.

The blast took place in the area of the boiler room at Zagorsk Optical and Mechanical Plant, in the town of Sergiev Posad, state news agency TASS reported. The plant is a developer and manufacturer for optical and optoelectronic devices for the Russian military, law enforcement agencies, industry and healthcare.

The source of the detonation was a pyrotechnics warehouse rented by a third company on the site of the plant, RIA Novosti said, citing local authorities. It described the incident as a violation of technological processes.

The blast was not caused by unmanned aerial vehicles (UAVs) -- military drones that Ukrainian and Russian forces have both used to launch strikes on enemy territory -- according to preliminary information, TASS reported.

Windows in several houses nearby were shattered by the blast wave, TASS added.

Two of the people injured were hospitalized, the Ministry of Emergency Situations said, reported RIA Novosti.

This is a developing story, more to follow...