The accident happened near St Tropez where firefighters had been battling to contain a 56ha blaze that had threatened villas and forced more than 4,000 people to evacuate.
The firefighters had been sent from Puget-Ville to fight the fire at Ramatuelle.
Meanwhile, Spanish fire authorities say they have managed to control most of the forest fires which have affected the north-west Galicia region. The fires have killed four people.
The Spanish timber industry estimates at least 100,000ha have been lost.
