The West Wyoming Borough Police Department investigated the discovery of three dead bear cubs and their nearly 300-pound mother in St. Monica’s Parish parking lot. The Pennsylvania Game Commission labeled the deaths as suspicious and called for public assistance.

The commission found no “signs of bullet wounds or external trauma.” Mark Rutkowski, Game Commission Northeast Region Law Enforcement Supervisor, said, “We consider the deaths of these bears highly suspicious. Toxicological testing will be performed in an attempt to determine a cause of death.”

Tests at the Penn State Animal Diagnostic Laboratory revealed the bears likely died from poisoning. The bears had consumed leaves and seeds of an English yew (Taxus baccata) plant, which contains the toxic alkaloid compound taxine. The toxicity of yew increases in winter, impacting the heart’s ability to beat properly.

“Organic chemical screens were performed on the stomach contents, liver, and kidneys of the bears to test for pesticides, euthanasia agents, and environmental contaminants. The results were all negative,” the department wrote on Facebook. The presence of yew leaves and seeds in their stomachs led to the conclusion that the bears died from plant toxin poisoning.