CHICAGO (CBS)– Dog owners in Morton Grove are uneasy this Christmas, after reports of “rat-poison-laced treats” scattered on a popular trail.

The warnings came from a Facebook post written by the Heartland Animal Shelter. The local animal shelter says two dogs are now fighting for their lives.

Donald Wojnicki walks his dog in Linne Woods Forest Preserve and said this incident “sick.”

Forest Preserves of Cook County police say they are actively investigating and sent out two shifts of officers to scour the trail. The police reported they did not find anything.

“It depresses me so much and scares me too, of course,” dog owner Sara Paretsky said.

John Rodriguez said he is going to be more careful and keep an eye out when walking his dog.

After reading the warning, resident Donald Wojnicki encourages others to report any incidents they see.

Officials say common symptoms of this type of poisoning include impaired movement and muscle tremors.

Anyone with information is asked to contact Forest Preserves of Cook County police.