The blaze spread across 15,000 square meters (3.7 acres), according to Berlin’s fire brigade.
Big explosions could be heard from the disposal site, which is used to defuse old military supplies from World War II, as well as fireworks and weapons, Berlin Fire Brigade Director Karsten Homrighausen told reporters.
”The situation is dangerous,” Homrighausen said, adding that around 120 firefighters were battling the blaze. ”It will take us some time to get everything under control.”
Earlier on Thursday, Berlin’s fire brigade called on residents to stay away from the Grunewald.
Due to the threat of further explosions from the ammunition site and flying debris, the fire brigade said it had not started to systematically extinguish the blaze as emergency services had to keep a distance at first.
Homrighausen went on to say that residential homes were not immediately threatened by the fire, but cautioned that the blaze could spread due to the dry conditions of the forest.
This comes as the country is bracing for one of the hottest days in 2022. Temperatures were expected to reach 38°C (100.4°F) on Thursday, according to the German weather service DWD, and Berlin is currently facing a weather warning.
Authorities in the city have called for additional task forces to help extinguish the fire, including special forces from the German army.
The blaze and the explosions also prompted local authorities to suspend rail transport and restrict road access in and around the Grunewald forest.
Munitions dating back to World War II are not uncommon finds in Germany.
In December 2021, four people were injured in an explosion caused by an old aircraft bomb near a busy train station in the German city of Munich.
It was not clear exactly when that bomb dated from, but more than 70 years after the end of World War II roughly 2,000 tons of live bombs and munitions are discovered in Germany each year, Reuters reported at the time.