Two amateur winemakers died last weekend treading grapes for home-made wine.
Daniel Moulin, 48, and Gérard Dachis, 50, of Roiffieux, northern Ardeche died from carbon dioxide poisoning.
They were crushing grapes in the traditional manner with their feet, in a vat that was approximately four square metres in size.
The grapes belonged to a small-scale winemaker who had recruited three friends to help vinify his 2008 vintage. The wine was intended purely for personal use.
It is thought that, with inadequate ventilation, they were rendered unconscious by the carbon dioxide fumes that are produced during fermentation. The two men did not regain consciousness, despite attempts to resuscitate them.
The owner of the estate, and the other friend who was helping with the winemaking, survived. A fireman and the third friend were also treated for inhalation of carbonic gas in a hospital in Annonay.
An autopsy to confirm the cause of death is due to be carried out this week, Le Post newspaper reports.
Written by Jane Anson in Bordeaux