Toronto police are warning the public of the dangers of fentanyl after as many as 100 patches of the fast-acting narcotic were reported stolen from a pharmacy.

The patches were reported stolen following a break-in at a pharmacy in the area of Queen and Church Streets sometime Wednesday night or Thursday morning, Toronto Police Det. Sgt. Mike Richmond said at a news conference Friday.

Between 14 and 20 boxes of fentanyl transdermal patches were stolen, he said. Each box contains five skin patches of various strengths.

Fentanyl is a strong pain medication often prescribed to palliative patients.

"The drug has been and continues to be a substance used by drug abusers," Richmond said.

"It is an extremely dangerous drug and historically has caused a number of deaths in Canada."

Richmond said the presence of the drug on the streets of Toronto is a "significant risk" to the public.

Last week, Toronto police said that the city didn't have as large of a fentanyl problem as seen in western Canada, but warned that drug trends can shift quickly.

Officers warned that dealers often mix fentanyl, which can produce a high up to 40 times stronger than heroin, with other substances. The Toronto Police Drug Squad warned that there is no way to know from looking at a pill or powder how much fentanyl it might contain.

At the news conference Friday, Richmond added that discarded skin patches will likely still contain traces of the drug, which can cause illness or death if touched or ingested. He recommended that anyone who sees one should avoid touching it, and immediately call police.

Richmond said that the boxes and patches were clearly marked as fentanyl. Anyone with more information is asked to contact police at 416-808-5104, or Crime Stoppers anonymously at 416-222-8477 (TIPS).