At least 45 people were injured in an explosion today at an optoelectronics factory in the town of Sergiev Posad, 50 kilometers northeast of Moscow, local authorities said.

Emergency services said the explosion appeared to have occurred in a warehouse containing pyrotechnic equipment, state news agency TASS reported.

Twenty-three of the injured were hospitalized, including six in intensive care units, the city’s mayor’s office said.

Videos and images on social media showed a huge plume of smoke rising into the sky above the crash site and broken windows in high-rise buildings.

The Zagorsk plant produces optical equipment for industrial uses, including in the healthcare sector as well as for the Russian security forces.

TASS reported that emergency services do not believe the explosion was caused by a Ukrainian drone strike, as several such attacks have taken place in and around Moscow in recent weeks and months.