A number of stray or feral cats have this week ingested what appears to be antifreeze, according to rescue groups, inciting fears someone might be intentionally poisoning the animals.

An estimated 20 deaths from two different cat colonies have been reported by cat caretakers in the communities. Many other cats are said to be sick, missing or dead, though the exact numbers remain unclear.

At least one of the colonies was completely wiped out, going from 20 cats to just one.

Five cats from a colony in the Jane Street and Weston Road area died, said Toronto Animal Services. Two were found dead and three were euthanized by vets because they were deemed too ill to survive.

Colonies are congregations of stray or feral cats which, in these cases, are fed by cat rescue groups and neighbours.

Dr. Esther Attard of the Toronto Animal Services said tests from autopsies on two cats showed ethylene glycol toxicity, consistent with common antifreeze, in the Jane and Weston colony. She is currently awaiting results on tests for other cats found dead this week.

She cautions, though, that the cats could have mistakenly consumed the antifreeze, and these are not necessarily an intentional poisoning.

Colony caretakers, however, say the incidents are too coincidental and too many cats have died for it to be unintentional.

The Toronto Feral Cat Project, an advocacy group for feral cats in the city, alerted colony caretakers to, "treat any threats made to the cats in your care and/or local colonies as a serious matter."