WARSAW, Poland (AP) — Polish authorities say an explosion at a black gunpowder plant in southwestern Poland has injured 17 people and left two others missing.

A spokesman for local firefighters, Jozef Koszalka, said Wednesday that the plant in Makolno, in the Wroclaw region, collapsed in the blast. Four of the injured were hospitalized with burns and firefighters were searching for the two missing people.

Army explosives experts have been called to check whether there is any threat of more explosions, while police and prosecutors were investigating the cause of the blast.