Public health officials in Kingston and surrounding communities are warning drug users to be cautious after five people have overdosed in the last two days on drugs suspected to be laced with fentanyl.

Dr. Fareen Karachiwalla, the region's associate medical officer of health, said that those who overdosed were not all taking opioids — at least one person used cocaine — and yet they required several doses of naloxone, an antidote to opiates.

Fentanyl is considered between 50 and 100 times more powerful than morphine, which is why it requires higher doses of naloxone to reverse its effects.

Karachiwalla said it's unclear if there are several batches of drugs that could be laced with the powerful opioid. But it's extremely unusual to see that number of people hospitalized for drug-related illness in two days, she said.

4 deaths in Toronto

Typically, about one person dies each month from a drug overdose in the Kingston region, Karachiwalla said. The area also includes Hastings, Prince Edward County, Lennox and Addington.

Officials in Toronto are responding to what some here have called a "public health emergency" following at least 20 overdoses last week, four of which were fatal.

That prompted Mayor John Tory to hold an emergency meeting Thursday. After it, officials said they would try to speed the opening of three upcoming supervised injection sites and see that firefighters in high-risk areas are trained to use naloxone kits by the end of September.