A spike in overdose incidents in London, Ont., is being investigated after a suspect allegedly handed out a free substance in the city’s downtown core.

Emergency services responded to 39 overdose-related calls between 8 a.m. Wednesday and 8 a.m. Thursday, with several people requiring medical treatment, London police said in a statement.

Investigators believe a potentially “toxic supply of illegal substances” may be circulating in the community.

The surge in overdoses was first flagged shortly after 11:15 a.m. Wednesday, when officers responded to reports of multiple non-fatal overdoses in the downtown area.

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Authorities learned that a suspect driving through the downtown core had distributed a free substance to several people before leaving the area.

Several individuals who ingested the substance subsequently overdosed and required medical care.

The investigation has been reassigned to the London Police Service criminal investigation division, where officers are working to determine the origin of the substance and identify those responsible.

Officials are urging anyone who may have received the substance not to ingest it and to contact police.

Residents are also being asked to provide dashcam footage or surveillance video from the downtown core that may assist investigators.

Authorities are reminding individuals of the risks associated with illegal drugs and are encouraging people not to use substances alone, to carry naloxone where possible and to call 911 immediately if an overdose is suspected.

Under the Good Samaritan Drug Overdose Act, individuals who seek emergency help during an overdose may receive some legal protection.

The investigation remains ongoing.

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