WARNING: This story contains details some readers may find disturbing.

GUELPH, Ont. -- Police say an "overwhelming" odour coming from an apartment in Guelph, Ont., has led to animal cruelty charges against a 19-year-old man.

Guelph police say the smell was so strong that the manager of the building believed a tenant had died in their home.

They say he repeatedly knocked on the door where he believed the smell originated, but didn't receive an answer.

Police say they were called on Monday afternoon and officers were immediately overwhelmed with a smell that permeated the entire floor.

They say they used a key to enter the apartment, where police say they saw a small white puppy and dozens of rotting piles of feces.

Police say the dog's rear end was matted and it was unable to pass its own waste. They say officers took the dog to the local humane society.

Zhenlin Lius Huang has been charged with mischief and causing unnecessary suffering to an animal.