One person is dead and “at least five” have suffered adverse effects caused by what police suspect to be a string of overdoses in downtown Toronto.

Toronto police responded to “numerous” overdose calls in the Strachan Avenue and Lake Shore Boulevard West area on Friday and Saturday, they said in a media release.

Police say that at least five people consumed unknown quantities of an unknown narcotic suspected to be an opioid. Every victim suffered adverse effects, and one died.

No description of the drug is available.

Investigators are concerned more of this drug may be sold or given to others. Toronto police reiterated in the release the importance of using extreme caution when taking drugs and never to use drugs alone.

If anyone suffers serious illness after consuming a narcotic, they should attend a hospital emergency room, call 9-1-1, or go to a walk-in clinic immediately for treatment.

Anyone with information about this drug or these suspected overdoses is asked to contact Toronto police.