Toronto Public Health (TPH) issued a drug use warning on Wednesday after at least 15 people died who consumed unregulated substances.

The city's health unit said it received several suspected opioid emergency calls that Toronto EMS received, all of which occurred in the past four weeks.

Also, according to Toronto's drug checking service, higher than usual concentrations of fentanyl were found in fentanyl substances, especially in the heart of downtown. Furthermore, the Drug Policy Evaluation Center, also known as, noted an increase in drugs associated with benzodiazepines and high-potency carfentanil in fentanyl samples.

Likewise, Public Health said that a range of substances were responsible for the fatal overdoses, which were distributed in a "variety of neighborhoods" across Toronto.

TPH said in its November 16 warning: "Fentanyl continues to appear in the local drug supply in a range of colors with unpredictable potency and contamination. The potency of fentanyl combined with carfentanil and benzodiazepine-related drugs may increase the risk of overdose, and additional support may be needed to revive individuals who are overdosing."

Also, people who use drugs are advised to try not to use drugs alone, use a supervised consumption service if possible, check their supply, verify what is in their drugs at local drug checking services, and obtain naloxone.

Additionally, those who use drugs alone are encouraged to have someone check on them in person or by phone, or consider calling the National Overdose Response Service at 1-888-688-6677 (NORS), or connect with community members virtually.