Berlin (CNN) A number of World War II munitions exploded as wildfires took hold in a forest around 40 miles southwest of Berlin, Raimund Engel, wildfire crisis administrator for the state of Brandenburg, told CNN Friday.

Firefighters initially could not enter the affected area because of munitions in the ground that exploded in the heat, Engel said, adding that the leftover ammunition is "scattered across the area" and the total amount of unexploded material is unknown.

The fire in the town of Treuenbrietzen began shortly after noon on Thursday. At least 550 firefighters, police and members of the military were called in to help control the flames, along with three helicopters, Engel said.

Residents in the village of Frohnsdorf were evacuated Thursday as the fires took hold.

A firefighter in action during the forest fire on Thursday.

More than 24 hours later, hundreds of firefighters were still fighting the blaze, but there was no longer any danger of it spreading further, according to Engel.

Around 400 hectares of forest were burning at the peak of the fire, the Brandenburg state chancellory said Thursday . Three nearby villages were evacuated.

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