Mink infected with coronavirus have been found at a farm in the Eure-et-Loire region of western France, and 1,000 mink at the farm will be culled, the French agriculture ministry said on Sunday.
Cases in mink have also been reported elsewhere in Europe, notably in Sweden, Greece and the Netherlands.
In Denmark, the virus was found to have mutated into a different strain, which experts feared could render a vaccine less effective if transmitted back to humans. Around 17 million mink are due to be culled there.
France started testing its four mink farms in mid-November.
"At this stage, tests have shown the virus circulating in an Eure-et-Loire farm," the ministry said. "A second farm is unscathed. Tests are still under way in the last two farms, with results expected during the week."