HAMMOND, Ind. (AP) — Officials in northwestern Indiana say parasites were to blame for the deaths of several swans around a former Federated Metals facility since last fall.

The (Northwest Indiana) Times reports Indiana Department of Environmental Management officials informed Mayor Thomas McDermott last month that the parasites not only impacted the body organs, but also reached the swans’ brains. Lead poisoning initially was suspected.

The newspaper says six of more than a dozen mute swans reportedly also had elevated lead levels in their kidneys. Tests for avian influenza, botulism and other toxins were negative.

Officials in January had said they were conducting more tests around the facility and were collecting samples from nearby George Lake.

Whiting Metals currently operates at the site of the former Federated Metals, which did smelting and recycling there.