According to the Berlin fire department, the fire spread to 15,000 square meters (3.7 acres).
Large explosions were heard at the burial site, which is used to dispose of old World War II military supplies, as well as fireworks and weapons, Carsten Homrighausen, director of the Berlin fire brigade, told reporters.
“The situation is dangerous,” Homrighausen said, adding that about 120 firefighters are fighting the fire. “It will take us some time to get everything under control.”
Earlier Thursday, the Berlin fire brigade urged residents to stay away from Grunwald.
Due to the threat of further explosions at the munitions depot and flying debris, the fire brigade said it did not begin systematic firefighting efforts as emergency services had to keep their distance at first.
Homrighausen went on to say that the residences were not in direct danger of fire, but warned that the flames could spread due to the dryness of the forest.
This is as the country prepares for one of the hottest days in 2022. Temperatures were expected to hit 38°C (100.4°F) on Thursday, according to the German meteorological service DWD, and a weather warning has now been issued for Berlin.
The city authorities called in additional operational groups to extinguish the fire, including the special forces of the German army.
The fire and explosions also prompted local authorities to suspend rail transport and restrict access to roads in and around the Grunwald Forest.
World War II ammunition is not uncommon in Germany.
In December 2021, four people were injured when an old aerial bomb exploded near a busy train station in the German city of Munich.
It is not known exactly when this bomb was released, but more than 70 years after the end of World War II, approximately 2,000 tons of live bombs and ammunition are found in Germany every year, Reuters reported at the time.