ANKARA, Turkey -- An explosion at a rocket and explosives plant in Turkey caused a building to collapse on Saturday, killing all five workers inside, an official said.

The explosion occurred at around 8:45 a.m. at the compound of the state-owned Mechanical and Chemical Industry Corporation, on the outskirts of the capital, Ankara, Gov. Vasip Sahin told reporters.

Sahin said the explosion was likely to have been caused by a chemical reaction during the production of dynamite. Prosecutors have launched a formal investigation, he said.

Gray smoke was seen rising from the compound as ambulances and fire trucks rushed to the area, private NTV television reported.

Shop and house windows in surrounding areas were shattered by the force of the blast, the report said.

Family members rushed to the compound for news of their loved ones, the station said.