This is stated by Pierre Ory, prefect of the Seine-et-Marne department.
On Monday, a smaller fire broke out in another part of the forest, and together the two fires have burned through around 2,000 hectares of land, French media report. Around 1,000 people have been evacuated from their homes.
600 firefighters are working to extinguish the fires. Firefighting aircraft have been deployed in attempts to bring the fires under control.
On Monday, two people were arrested on suspicion of starting the fires in Fontainebleau.
