(Sacramento, CA) — Wildlife officials are investigating the deaths of several swans in a park in Sacramento County. Earlier this week, at least nine birds were found dead in and near Mather Lake in Mather Regional Park. Three to four swans were found dead in the lake itself, with another five to six found dead in the grass near the water.

The California Department of Fish and Wildlife was called in and took samples to determine a cause of death. Results of the tests are pending. Wildlife officials are planning to safely remove the swan carcasses from the lake this week to prevent contamination to the ecosystem.