Montreal police say they don’t believe any foul play was involved, but are evaluating a man after the decomposing body of his 85-year-old mother was found in an apartment in Cote-des-Neiges.

The building's janitor was carrying out emergency repair work inside the building on Barclay Ave., near Decelles Ave. and said he detected a very strong odour when he knocked on the door of the apartment.

The tenant opened his door, but the janitor became suspicious of the smell and called police.

Crime scene investigators spent the evening at the scene wearing protective equipment because they found the woman in an advanced state of decomposition.

An autopsy will determine a cause and time of death.

Evidence was hard to obtain because the son was unable to answer the most basic questions.

“It seems that we might face mental issues at this moment. The 45 year-old man was transported to the hospital,” said Montreal police spokesperson Raphael Bergeron.

He has been sent for a psychiatric evaluation, Bergeron explained.

One neighbour said the elderly woman had been looking after her mentally disabled son for some time. Police suspect the mother may have died of natural causes, leaving her son unable to deal with the situation, in the absence of other relatives.

Another resident said he never noticed any odd smell coming from the apartment where the man lived, adding that the woman moved in a few years ago and that he "rarely, rarely saw the woman."

Police are not yet treating this death as a crime.

“Nothing seems to be criminal, obviously we're going to have to wait until the autopsy. The body was in bad shape,” said Bergeron.

The police are hoping the woman's son will eventually be able to provide more information, but they'll have to wait until he's seen by mental health experts.