Dozens of dead vultures discovered at the Conowingo Dam between Cecil and Harford counties over the weekend are being tested for avian influenza, according to Constellation Energy, which manages dam operations.

The Maryland Department of Agriculture confirmed the first case of avian influenza in Anne Arundel County earlier this month, detected in a backyard flock of about 40 chickens.

Avian flu, commonly known as bird flu, is a highly contagious airborne respiratory virus that spreads among poultry and other birds through nasal and eye secretions, as well as manure. The virus can be spread from flock to flock, including by wild birds, through contact with infected poultry, by equipment and on clothing and shoes of people around the animals.

Constellation spokesperson Brandy Donaldson said personnel promptly notified Maryland DNR after discovering the carcasses on Friday, and dozens more were collected over the weekend. Most were on the Wildflower Trailhead and the Mason Dixon Trail between the overlook parking area and Fisherman’s Park, the release said. No dead birds have been found near the fishing wharf or at the dam itself.

While Fisherman’s Park remains open, Constellation has temporarily closed the Wildflower Trailhead and a section of the Mason Dixon Trail to prevent possible spread of H5N1 avian influenza. Maryland DNR is currently testing the carcasses.

“We are following safety protocols that are intended to assist with preventing HPAI spread. We will reopen these areas when it is prudent to do so,” the release said.

As Constellation considers reopening the trails, the company is working with state and federal agencies, including the U.S. Fish and Wildlife Service, the U.S. Department of Agriculture, the Maryland Department of Environment and Maryland Department of Agriculture.

The release said wild birds can carry HPAI without showing symptoms. Since infected birds might not appear ill, the public is advised to avoid contact with wild birds, particularly dead birds or those behaving erratically. Anyone who encounters a sick or dead bird should report it to on-site security or to the USDA.

In 2022, more than 100 vultures were found dead near the Conowingo Dam as a result of an avian flu outbreak.

The virus affects chickens, ducks, and turkeys along with some wild bird species such as geese, shorebirds and raptors. Outbreaks have also been confirmed in dairy herds. The risk of transmission between birds and humans is low, according to the Centers for Disease Control and Prevention.

This story may be updated.

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