Toronto Public Health has issued a drug alert after a new single-day record was set with five suspected opioid overdose deaths.

Between May 2 and May 6, TPH said Toronto Paramedic Services responded to 13 fatal suspected opioid-related overdose calls, including the five fatalities on Wednesday. The health unit noted it is the “worst cluster” of suspected overdose deaths since they began collecting data in 2017.

“These fatal calls have occurred across Toronto,” TPH said.

“The tragic loss of 13 lives highlights the unpredictable nature of the unregulated drug supply.”

TPH said supervised injection sites are also reporting an increase in overdoses. At the same time, they are noticing a growing number of “unexpected substances of concern” in the drug supply.

For the first time, etonitazene, an opioid known to be more potent than fentanyl, was discovered in the unregulated drug supply, prompting the city’s Drug Checking Service to issue an alert.

It was found in a sample, a brown powder, that was collected in downtown Toronto.

According to the Drug Checking Service, etonitazene offers effects similar to morphine and fentanyl, and due to its strength, the chance of overdose is increased.

Also, Toronto Public Health said they are hearing reports of heavy sedation linked to the consumption of yellow fentanyl.

TPH has said the opioid crisis has been compounded by the COVID-19 pandemic.

In January, the city set a grim new record of overdose deaths in a month with 38.