A fire broke out in Berlin's Grunewald forest early on Thursday following an explosion at a munitions storage site, with the German capital still facing searing summer temperatures. 

Additional explosions were heard Thursday evening, local media reported.

Firefighters were still fighting to contain the flames and will reassess the situation on Friday.

The threat of further explosions and flying debris meant firefighters were hampered from systematically extinguishing the fire. Personnel were forced to keep a distance of a kilometer (more than half a mile) from the flames.

Berlin fire department spokesman James Klein explained to DW the challenge that was facing firefighters.

"What we have here is an ordnance site. So ordnance is stored and also fireworks and other objects that can also explode, detonate."

"There are different items stored there, so there can be smaller and larger explosions. We are optimistic, because the heavy ordnance also located there, is stored accordingly, cooled and in steel containers, so that we can protect them."

Homes were not directly threatened by the fire, although the officials warned that dry conditions and the exceptional heat expected on Thursday meant that the blaze could spread. However, firefighters said they would prevent damage to properties.

Klein explained that the fire brigade would form a ring around the exclusion zone so they were ready to tackle the fire as it spread. 

"We now have fire engines positioned all around the 1,000 meter radius and then, when the fire gets to the radius, we can also start the firefighting work directly, so that the fire doesn't get out of hand there," he said.

"The forest is bone dry," said Jan Thomsen, spokesman for the Berlin Senate's Department for Environment, Mobility, Consumer and Climate Protection.

By the evening, the fire had spread 50 hectares, but authorities expect to contain the blaze completely overnight.

Fire impacted rail operations, Autobahn

National rail operator Deutsche Bahn said that the fire was having an impact on local and long-distance trains. 

A stretch of Autobahn highway between Spanischer Allee and Hüttenweg was also closed in both directions, as were two smaller streets, according to the local traffic authorities. Fire authorities said it was likely the section of road — known as the AVUS — would remain closed for the rest of Thursday.

A police spokesman said it was not yet clear how the explosions had taken place. The site is used to store and conduct controlled explosions of ammunition or weaponry secured by Berlin police's weapons disposal units. 

Berlin Mayor Franziska Giffey visited the scene later on Thursday, labeling the events "unprecedented in the post-war history of Berlin." She thanked emergency personnel for containing the blaze.

The 3,000-hectare Grunewald is one of Berlin's largest green spaces, starting on the western edge of the city and stretching out towards Potsdam. 

msh,rc,wd/jsi (AFP, dpa)

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