Some 10,000 square metres of one of the German capital's most extensive city forests have been affected, while the situation remains dangerous.
A large fire in one of Berlin's largest city forests, caused by several explosions at an ammunition dump, was still not under control by Thursday afternoon.
Around 100 firefighters were on site earlier to control the blaze in the Grunewald forest in the west of the city, German news agency dpa reported.
Berlin police said it was assisting their colleagues, setting up roadblocks to the forest and employing their own helicopters and water cannons in the fight against the fire amid concerns about its uncontrolled advance.
"The situation is dangerous," Thomas Kirstein from the Berlin fire department told reporters. He called on residents to stay away from the forest.
The fire first affected some 15,000 square metres, or 1,5 hectares of the forest, the city firefighting unit said on Thursday morning, while a one-kilometre perimeter has been set up as the situation remains high-risk.
The fire was spreading quickly, and massive explosions could be heard from the site where old ammunition from World War II, fireworks and explosive ordnance are stored, and controlled explosions are carried out.
The site has been in use since 1950, and the city has been looking for alternatives, but those were not available in the Berlin area and could not be approved, Berlin police said.
Due to flying debris and the threat of further explosions, the authorities said the responders were working on a "cautious containment" operation that could last until Thursday evening.
Berlin authorities called for additional help in extinguishing the flames, including special forces from the German army.
The commuter train service to the city's west was partially interrupted, and one of the city's most important highways, the Avus, was closed.
Homes were not directly threatened by the flames, but the fire department warned that the fire could further spread due to the dry conditions of the forest and the exceptional heat that was expected on Thursday with temperatures of up to 38°C.
The Grunewald forest covers around 3,000 hectares of land, and it stretches along the western part of the city along the Havel river.
The Berlin region is suffering from a particularly severe drought as well.
A large forest fire in July burned more than 850 hectares in southern Brandenburg, the region surrounding the capital. A little further south, a fire in the "Bohemian Switzerland" national park, which started in the Czech Republic and spread to Germany, is still keeping firefighters busy.