Public health officials in the Quebec City region are warning the population after three people died recently from fentanyl overdoses.

Eight more people suffered non-fatal overdoses from the synthetic drug in Quebec City. It comes during a wave of overdoses across the country.

Health officials and addiction workers in Montreal are on high alert.

So far there have been no reported overdoses in Montreal recently, public health officials said, adding that it could be possible.

Some studies show the analgesic and sedative can be up to 40 to 100 times stronger than morphine.

When purchased illegally,  users most likely believed they were buying oxycodone or other types of opiates.

Health officials warn the pills are often blue, marked A215.

Quebec's public health agency said people who overdosed there were between 19 and 44 years old.

"We know that fentanyl is a drug that is very toxic and dangerous when it's not used as prescribed by a doctor, so when you buy fentanyl on the black market, in the street, you never know what you're actually buying and it's very toxic and dangerous," explained Nathanaelle Theriault of Quebec City's public health agency.

Montreal outreach workers are advising drug users to be especially cautious and to not use alone.

Last year 15 people died in Montreal due to overdoses possibly linked to fentanyl.