France, Sept. 29 -- The apparently pristine Gerardmer lake in the Vosges mountains of eastern France conceals a bleak legacy of 20th-century conflict- dozens of tonnes of unexploded ordnance from the two world wars.

The lake 660 metres above sea level is a popular summer bathing spot and is sometimes also tapped for drinking water for the picturesque local town.

Gerardmer's mayor Stessy Speissmann-Mozas started asking questions about the water safety after the Odysseus 3.1 environmental group said samples taken from the lake showed high levels of TNT explosive, as well as metals like iron, titanium and lead.

The group said it found artillery shells in the mud at the bottom of the lake. Some were "gutted, allowing the explosive they con...