Firefighters have been having difficulty getting close to the flames because parts of the wildfires are on a former military training area where there is a risk of ammunition detonating.
At least two firefighters have been seriously injured and more than 100 residents evacuated as wildfires continue to burn in eastern Germany.
Nearly 500 firefighters have been deployed to battle the blazes that broke out on Tuesday in Gohrischheide on the border between the eastern states of Saxony and Brandenburg.
One female and one male firefighter suffered burns during the firefighting operation.
The fires have ripped through hundreds of square kilometres and by Thursday had still not been brought under control.
A state police helicopter equipped with special cameras to detect pockets of embers is being used, the German news agency dpa reported.
Firefighters were having difficulty getting close to the flames because parts of the wildfires are on a former military training area where there is a risk that ammunition stored there could detonate.
The villages of Heidehäuser and Neudorf and parts of the village of Lichtensee have been evacuated.
Residents received mobile phone alerts directing them to only take essentials, especially identification and cash.
The notice advised them to inform neighbours and "cover your mouth and nose with improvised respiratory protection (cloth, piece of clothing, surgical mask)."
District officials called on people travelling by car to avoid the region.
An African anticyclone is sweeping across Europe, leading to record temperatures of up to 46 degrees Celsius in some countries.
That severe heat has led to several wildfires across the continent.