A fire that swept through part of the Fontainebleau forest, one of France's best-loved woodlands about 60km south-east of Paris, has taken a startling turn: among those arrested is a young volunteer firefighter suspected of helping to start it.

The 18-year-old was placed under formal investigation and held in custody after, according to prosecutors, initially telling investigators he had set light to twigs using a lighter and petrol. He later retracted that account. Under French law, being placed under formal investigation means there is serious evidence to justify further inquiry; it is not a conviction, and the young man is presumed innocent.

A forest ablaze

The blaze burned through roughly 2,000 hectares of the forest, which surrounds the Château de Fontainebleau, a former royal residence and a major draw for tourists and walkers. Around 1,000 residents were evacuated from nearby communities as the flames spread in hot, dry conditions, and a stretch of the A6 motorway linking Paris to the south-east was closed, as reported by broadcasters covering the emergency. Hundreds of firefighters, backed by water-bombing aircraft, fought for days to bring it under control.

The episode is part of a wider spell of fire danger across France, where an intense summer heatwave has left forests tinder-dry and put many areas on high alert. Earlier in the month, separate wildfires forced thousands to flee in the south of the country.

Shock within the fire service

For France's firefighters, the suspicion that one of their own volunteers may have been involved has been especially painful. Fire service officials described being in deep shock, and the young man was suspended from his duties. In all, six people have been arrested in connection with fires in the region; a second person, also a teenager, is reported to have said a blaze at another site was started accidentally by a discarded cigarette.

Authorities have not disclosed any confirmed motive, and the investigation is continuing. Cases in which firefighters are accused of setting the very fires they are meant to fight are rare but not unknown, and they tend to draw intense public attention precisely because they cut against the trust placed in the emergency services.

A vulnerable landscape

The Fontainebleau forest is prized for its ancient trees, sandstone boulders and rich wildlife, and any large fire there causes lasting ecological damage as well as immediate danger. Its closeness to Paris made this blaze unusually visible, with smoke drifting over a densely populated region and transport links disrupted.

As France endures a summer of heat and heightened fire risk, the case is a reminder that not every wildfire is purely a product of the weather. Whatever the courts eventually conclude about the events at Fontainebleau, the damage to a cherished landscape, and the unease within a proud emergency service, will take time to heal.