Three bald eagles have died after at least 13 of the birds were likely poisoned from scavenging the carcasses of euthanized animals that were dumped at a Minnesota landfill, according to experts.

The eagles were found last week near the Pine Bend Landfill in the Minneapolis suburb of Inver Grove Heights, the Minneapolis Star Tribune reported.

Local police first found one sick juvenile eagle in the snow on Dec. 4 and brought it to the University of Minnesota Raptor Center, the center posted of Facebook.

Its medical staff determined the bird was likely suffering from pentobarbital poisoning, the primary agent used in euthanasia solution.

The center was alerted about a second eagle found in similar condition at the landfill the following day. However, volunteers arrived and discovered nine more sick eagles. Two other eagles were found dead near the landfill.

Ten of the birds remained in intensive care at the Raptor Center. The center’s executive director Victoria Hall told the paper she is optimistic those birds will recover.

Veterinarians suspect that the eagles that died had eaten part of a carcass of an animal that had been euthanized with pentobarbital, and investigators confirmed that some euthanized animals had been brought to the landfill on Dec. 2.

Hall said animals that have been chemically euthanized are supposed to be disposed of in such a manner that other animals can’t scavenge on them.

Of the 11 eagles that were brought to The Raptor Center, three also had lead poisoning and one eagle that was found to have bird flu died.

The Associated Press contributed to this report.