COPENHAGEN, Denmark -- The carcasses of almost a dozen cows have washed ashore in Denmark and Sweden, puzzling police in the Scandinavian countries.

Since Dec. 29, eight dead cows have been found by people strolling on beaches in southern Sweden and three in Denmark. All the animals had parts of their ears cut off. Investigators suspect this was done to remove the identification tags used to trace the cows.

Danish and Swedish police said Thursday the cows were probably dumped from a ship in the Baltic Sea. They are trying to pinpoint which livestock transports have passed through the waters separating the two countries in recent weeks.

Dumping livestock like that is illegal in both countries. It's unclear, however, whether the cows were thrown overboard in Danish, Swedish or international waters.

Some of the cows had their back legs tied together with a blue rope, Danish police officer Boje Joergensen said, adding it was probably done to be able to lift the animals up with a crane.

Veterinarians in Sweden found no traces of disease in the animals washed ashore there, Swedish police said.

Police believe the cases are related as the cows were all black-and-white Holsteins.