An explosion at a Russian factory outside the capital Moscow on Wednesday has injured at least 52 people, the region's governor said.
Officials in the city of Sergiyev Posad, some 35 miles (56 km) north-east of the capital, said the blast occurred at a plant that produced optical equipment.
"Now 52 people have sought medical help," Moscow region governor Andrey Vorobyov said on state television.
"Some have slight contusions from the blast wave, some just have burns."
Video shared by state media showed a bright ball of flames burst on the horizon, followed by a shockwave that blew out windows from some buildings.
Vorobyov said he could not comment on the cause of the explosion but that it was being investigated.