An explosion occurred at a factory of optical-mechanical machines in the city of Sergiev Posant, 50 km northeast of Moscow, on Wednesday, injuring at least 16 people, as reported by Reuters citing TASS.

The factory in Sergiev Posad produces optical equipment, with Russian security forces as customers.

However, TASS citing emergency services say they do not suspect the explosion was caused by a Ukrainian drone strike, many of which have taken place in and around Moscow in recent weeks and months.

Reuters reported that the explosion appeared to have occurred in a warehouse containing pyrotechnic equipment. Popular online news channel Mash reported that the warehouse had been rented by a fireworks company.

Unverified footage on social media showed a huge plume of smoke and high-rise buildings with glass.