There were 12 overdoses in a 24-hour period in Guelph from Aug. 1 to 2, according to Wellington-Dufferin-Guelph Public Health.

The agency posted on Facebook on Friday to say that the overdoses were "likely to be related to fentanyl, which seems to be extremely potent."

Police and EMS issued an alert after responding to four cases on Friday morning.

They reminded people to call for help if they suspect someone has overdosed.

"Should you discover a friend or loved one unconscious for an unknown reason, please don't hesitate to call 911. You may save their life," police said in a release.

On Facebook, the Guelph Community Health Centre notes the supervised consumption site is open all weekend, including the holiday on Monday, between 10 a.m. and 4:30 p.m.

Police said while they "discourage the use of illicit street drugs" people who do take drugs should use "extreme caution."

"You are strongly encouraged to go to the supervised injection site and/or have naloxone and a second person present who can assist in its administration," police said.