VANCOUVER -- A number of squirrels have been reported sick or dead this month after a "toxic substance" was left in a park in Richmond, B.C., according to police.

Richmond resident Stephanie Payne says two of her friends were out for a walk in South Arm Park last Wednesday, when they came across multiple squirrels either deceased or in grave condition.

"They saw five squirrels that were pretty much almost dead," she said

One of the women immediately reported the distressed squirrels to the BC SPCA and the City of Richmond, which prompted firefighters and city staff to cordon off parts of the area for public safety.

Firefighters scoured the park and discovered a toxic chemical around some of the trees. The compound, known as 1-octanethiol, can cause headaches and vomiting in humans. If handled incorrectly, it can be deadly.

“We want to know who put it there and why it was put there,” says Cpl. Adriana O’Malley, spokesperson for Richmond RCMP.

Police confirm the toxic material has since been safely removed by an environment clean-up crew and the park is fully reopened.

As investigators search for a motive, Payne has her own suspicion of why a toxic substance was dumped in the park. She has frequented the greenspace for the past five years and in that time, she says the squirrel population has grown significantly. Payne believes someone must be fed up with the critters.

“There was so many," she said. "Now, I walk the park and am like why am I not seeing any squirrels? It’s just really odd.”

Payne’s friends have put up posters on trees throughout the park, warning pet owners and people with young children about the harmful chemicals. They’ve also spread the word in community groups online. Richmond RCMP is urging park users to be vigilant.

“If you’re going to the park and you start to see wildlife that appears sick or you’re finding deceased wildlife, make sure you contact the city of Richmond of police,” says Cpl. O’Malley.

Mounties says the chemical has not been found in any other parks so far, and there have not been any reports of people or family pets falling ill.

Anyone who has information on the incident, or who witnesses someone dumping substances at the base of trees in Richmond, is asked to call the RCMP at 604-278-1212. People who want to remain anonymous can instead call Crime Stoppers at 1-800-222-8477.