Residents of three villages outside Berlin have been forced to evacuate to escape several forest fires threatening to burn out of control.
"The fire continues to be a big threat", Mr Woidke said.
Large swathes of the forest are considered too unsafe to access on foot, Bild reported, given the danger of unexploded hand grenades and shells, some of which have already been set off by the fire.
Local lawmaker Christian Stein said there had already been several detonations due to the ammunition, and that firefighters were not allowed to enter suspicious areas.
The fire started on the afternoon of August 23 and spread quickly through the dry pine forests in the Treuenbrietzen region, 50 kilometers (30 miles) outside of Berlin in the eastern state of Brandenburg.
"The ammunition is very unsafe, because one can not step on the ground, and therefore one can not get close to the fire" to extinguish it, Brandenburg state's governor, Dietmar Woidke, told reporters.
Hundreds of people have been evacuated from homes menaced by the fire. Instead, the authorities were trying to douse the flames in those areas with firefighting helicopters and water cannons. "But we will do everything to protect people's property".
About 500 people have so far left their homes in the villages of Frohnsdorf, Klausdorf and Tiefenbrunnen.
Winds have blown smoke from the fires north to Berlin, where the fire service issued a warning to residents Thursday evening.
Germany has had nearly no rain this summer, and hundreds of firefighters and soldiers have been sent to all parts of the country to tackle wildfires.
"The fire services are very anxious that the wind is constantly changing, which could cause areas they think have already been extinguished to burst into flames", Woidke told reporters Friday morning.
The city was still affected Friday morning, when the fire service advised residents to keep doors and windows closed.
Raimund Engel, an official tasked with handling forest fires on behalf of Brandenburg, the state where the fire broke out, said the wind had dropped making it easier to contain the fire.
Germany has seen a long, hot summer with nearly no rain, and large parts of the country are on high alert regarding possible wildfires. "We are yearning for rain".