Repeated explosions have prevented firefighters in Berlin from reaching a blaze in a forest to the south-west of the city that started at a police munitions site used to store second world war bombs.
The fire broke out in the early hours of Thursday morning after unexploded ordnance was accidentally detonated, according to the Berlin police.
The forest, in the well-to-do Grunewald district of the German capital, is popular with city dwellers, from swimmers to dog walkers.
The fire took hold in an area about 1.5 hectares (3.7 acres) in size. Approximately 100 firefighters are at the site, but were unable to get within 1,000 metres of the flames because of a series of explosions triggered by the heat.
The Berlin fire brigade said drought-like conditions had already made the forest susceptible to fire. An unprecedented number of forest fires elsewhere across Germany also means there is a shortage of fire-fighting helicopters to tackle the blaze.
The police site is used to store unexploded ordnance, ranging from confiscated illegal fireworks to second world war munitions that are regularly discovered at building sites across the city.
Controlled explosions are periodically carried out by experts at the site to safely dispose of stock but no detonations have taken place since June because of the dry conditions, resulting in more explosives being stored there than is usual.
The fire also closed a stretch of the overground S-Bahn railway, bringing disruption to public transport across the city and disrupting long-distance trains to Amsterdam, and closed the Avus autobahn.
The nearest residential building was nearly 2 miles away and people in the area were urged via mobile phone warnings and radio broadcasts to close windows and doors and turn off air conditioning appliances. Clouds of thick grey smoke dominated the skyline and the sounds of explosions were heard over several miles. No injuries were reported.
The police and fire services were using drones and helicopters to gauge the development of the fire and carrying out containment measures to stop it spreading, including watering the edge of the forest. A spokesperson said three separate blazes had been identified.
The intensity of the heat was holding forces back he said, adding that there was a need to frequently bring in fresh firefighters because of heat-related exhaustion. Reinforcements have been called from other parts of Germany.
Jan Thomsen, of Berlin’s environment department, said the lack of rain meant the fire was able to take hold quickly.
He said the forests were bone dry and had “not been able to recover due to the long periods of drought.” Asked by reporters whether it was sensible to have an explosives site in a forest, he said: “We will have to deal with these safety questions once the cause of the fire has been ascertained”.