Toronto Public Health (TPH) has issued a drug alert after “at least” 15 people who consumed unregulated substances died.

The city’s health unit said Toronto Paramedic Services responded to a total of 25 fatal suspected opioid calls between October 18 and November 15.

They said during that four-week timeframe there were three separate four-day "clusters" during which an average of five people died of an overdose. This is higher than normal, TPH told CP24.com in a follow-up note.

The first cluster occurred from Oct. 18 to 21. The second was from Oct. 25 to 28, and the third was from Nov. 10 to 13. 

According to Toronto’s drug checking service, higher-than-usual concentrations of fentanyl were found in fentanyl substances, especially in the city’s downtown core.

Further, the Centre of Drug Policy Evaluation, as it’s also known, observed an increase in benzodiazepine-related drugs and highly potent carfentanil in fentanyl samples.

A range of substances were involved in the fatal overdoses, which happened in a “variety of neighbourhoods” throughout Toronto, said public health.

“Fentanyl continues to show up in the local drug supply in a variety of colours with unpredictable potency and contamination,” TPH said in its Nov. 16 alert.

“Higher potency fentanyl in combination with carfentanil and benzodiazepine-related drugs may increase the risk of overdose, and additional supports may be required to rouse individuals experiencing an overdose.”

People who use drugs are being advised to try not to consume drugs alone; use a supervised consumption service, if possible; vet their supply; check what's in their drugs at local drug checking services; and get naloxone.

Those who consume drugs alone are being urged to get someone to check on them in person or by phone, consider calling the National Overdose Response Service at 1-888-688-6677 (NORS), or connect with community members virtually.

“Always call 911 when somebody is experiencing an overdose, especially if someone is not responding to naloxone,” TPH noted.