ISTANBUL (AP) — A truck carrying fireworks exploded in northwestern Turkey on Thursday, killing three military police officers and wounded six others, officials said.

The fireworks, which were from a factory where an explosion last week killed seven people, were being transported to be destroyed in a controlled explosion in Sakarya, the Interior Ministry said in a statement. The material exploded as it was being taken off the truck, and two of the dead were from the bomb disposal unit of the military police, the ministry said.

Sakarya Gov. Cetin Oktay Kaldirim said one of the injured was in critical condition and that the fireworks and explosives were to be destroyed in a quarry. Television footage showed a destroyed truck in a blackened pit, fire trucks and ambulances.

The explosion follows a huge blast July 3 at the fireworks factory in Sakarya that killed seven people and injured more than 120. The cause of the blast at the factory, which is away from residential areas, was under investigation. A factory owner and four employees were arrested.