Warsaw - Two people were killed and 15 were injured in an explosion at a black gunpowder plant in southwestern Poland, local authorities said on Wednesday. A spokesperson for local firefighters, Jozef Koszalka, said that the plant in Makolno, in the Wroclaw region, collapsed in the earl-morning blast. Four of the injured were hospitalised with burns. Earlier, firefighters estimated the number of the injured at 17.Ilona Golec of local police said two people were confirmed dead. Army explosives experts said there was no threat of more explosions after the site was sprayed with water. Police and prosecutors were investigating the cause of the blast.