VANCOUVER - The City of Vancouver says its first responders are attending to an increasing number of calls linked to deaths or overdoses caused by illicit drugs.

City officials say five overdose deaths were recorded in Vancouver during the week of June 12, up from four the week earlier.

Vancouver Fire and Rescue Service reports an 18 per cent increase in overdose calls over the same period.

A news release from the city says a local medical lab has also identified a spike in the number of urine samples testing positive for carfentanil, an opioid considered to be 100 times more powerful that fentanyl.

Twenty-one per cent of samples tested by the lab showed signs of carfentanil, up from six to eight per cent of samples tested in February and March.

The city says the increase presents "an extreme risk" to the public.