The fire has spread over 15,000 square meters (3.7 acres), according to the Berlin fire department.
Large explosions could be heard from the disposal site, which is used to defuse old World War II military supplies, as well as fireworks and weapons, the director of the Berlin fire department told reporters. , Karsten Homrighausen.
“The situation is dangerous,” Homrighausen said, adding that about 120 firefighters were battling the blaze. “It will take time for us to master everything.”
Earlier Thursday, Berlin firefighters called on residents to stay away from the Grunewald.
Due to the threat of further explosions from the munitions site and flying debris, firefighters said they 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 at risk from the fire, but warned that the fire could spread due to dry conditions in the forest.
It comes as the country prepares for one of the hottest days of 2022. Temperatures are expected to hit 38C (100.4F) on Thursday, according to German weather service DWD, and Berlin is currently facing a weather warning.
City authorities called in additional task forces to help put out the blaze, including German army special forces.
The fire and explosions also prompted local authorities to suspend rail transport and restrict road access in and around the Grunewald forest.
Munitions dating from the Second World War are not uncommon in Germany.
In December 2021, four people were injured in an explosion caused by an old plane bomb near a busy train station in the German city of Munich.
The exact date of this bomb was unclear, but more than 70 years after the end of World War II, around 2,000 tonnes of live bombs and munitions are discovered in Germany every year, Reuters reported at the time. .