The farm in the village of La Puebla de Valverde in the region of Aragon, 200km east of Madrid, came to the attention of the authorities after the wife of one of its workers tested positive in May.

Joaquin Olona, head of the Aragon agriculture department, told reporters on Thursday that seven farmworkers had subsequently tested positive, including the woman’s husband.

Authorities initially ordered that the animals should be isolated. But a few weeks later, after several rounds of testing, they decided to cull the mink, which are farmed for their fur. As many as 80% of a sample of the animals tested positive.

The management of Secapiel, the company that runs the region’s only mink farm, was not immediately available for comment. The company will receive financial compensation for the culling, authorities said.

The virus has proven contagious in several types of mammals including cats and dogs.

Cases of mink with coronavirus were identified in Denmark, the world’s largest producer, and the Netherlands and, even though the animals did not show any symptoms, hundreds of thousands were culled to prevent farmers becoming infected.