POLICIA Nacional agents have arrested five people and rescued 270 Chihuahuas and Pomeranians bred in illegal kennels close to Madrid.
The gang, two of which are vets, were alleged to have been the leading distributor of puppy dogs around Spain and Europe.
The dogs were found hidden in a filthy basement, many with their vocal cords cut to restrict barking.
Authorities were first alerted early in 2019 by a neighbour living close to one of the two properties, in the Madrid towns of Meco and Arganda del Rey.
Investigations revealed the dogs were sold throughout Spain via the internet.
Agents revealed the young dogs were kept in poor sanitary conditions, and that indiscriminate breeding without any veterinary control generated multiple medical conditions for females.
Two were found dead, frozen and wrapped in newspaper.
It is believed the group had been operating for more than a decade, generating over two million euros in income.
The animals are now in the custody of several protection agencies, pending the judicial decision on their ultimate fate.