A French ordnance disposal experts have discovered dozens of World War II grenades in an area ravaged by the major forest fire on the country's Atlantic coast.

"We were on a mission last week and found this field, where we removed 75 shells," Philippe Delemotte, head of the Bordeaux explosive ordnance disposal service, told broadcaster France Info on Monday.

"Today we waited a while until the field had cooled down so we could enter it. And within a few minutes, we found more shells like these here."

Explosions had been heard in the village of Le Porge while France's largest wildfire of the season so far ravaged the area, leading to the discovery of the projectiles.

The team initially thought they had discovered a munitions cache left behind by German troops.

However, Delemotte said they later concluded that the grenades had been indented to be destroyed in dug-out pits. However, the operation had not entirely been successful, he added, with live grenades left behind on the surface.

To ensure that residents could return safely to the adjacent homes, the remaining grenades are being located and rendered harmless as quickly as possible, he said.

According to Delemotte, the finds include French mortar shells and German tank shells. "We can assume there are still many more of them, as we've already found several within five minutes," he said.