"It is not under control," Interior Minister Laurent Nunez said late on Monday, adding that the main blaze in Fontainebleau and another one nearby that started on Monday afternoon had scorched 1300 hectares.
Nunez said the fire was just a few kilometres away from the Palace of Fontainebleau, which explained the deployment of considerable resources, including water-carrying planes and helicopters.
For the first time, Canadair aircraft on Monday skimmed the River Seine to fill their tanks, attempting to contain a blaze that turned the sky black.
Just 70km from Paris, the fire forced the closure of the A6 highway linking the capital with Lyon and the south.
Smaller fires in the area also disrupted high-speed train services.
As many as 900 people fled from their homes.
Nunez said the Fontainebleau blaze was contributing to what would likely be a historic year for fires in France, with 32,000 hectares burned already in 2026, more than the total in 2025.
"We'll probably have a record year," he said.
"We expected this with this major drought."
Europe is enduring its third heatwave of the summer, with tinder-dry vegetation and high temperatures fuelling blazes from the Iberian Peninsula to France.
Many scientists say climate change is making wildfires more frequent and difficult to combat.
Nunez said 59 people had been arrested across France on suspicion of starting fires across the country.
About half were adults and half minors, with some repeat offenders, he said.
