BARRIE, ONT. -- The Grey Bruce Health Unit is sounding the alarm over an ongoing trend in opioid overdoses after three deaths in a single week.

In one instance, a grey chalk-like product is suspected as the cause. Health officials believe fentanyl or carfentanil could be to blame, but note substances of differing colours, including yellow, purple, green, and pink.

The health unit adds, "smoking these products causes near-instant collapse and in some cases, death."

Harm Reduction Manager Ian Reich says younger people are experimenting with dangerous street drugs. "In recent cases, multiple doses of naloxone were not sufficient to reverse the overdose, and as such, someone lost their family member."

Reich advises parents to talk with children about the risks. "And if you don't know how to talk to them, call me. I will talk to them. They need to be aware. We all need to be aware."

Users are urged to avoid doing drugs alone, avoid mixing drugs and alcohol and know their tolerance.

Those who use alone are encouraged to call the Overdose Prevention Line at 1-888-688-6677. The phone service provides live, safe contact while using. In the event someone becomes unresponsive, the operator will call for help.

The health unit reports at least eight fatal overdoses this year in communities across the region.