Vancouver police have issued a warning to local drug users about a potent batch of heroin that authorities believe has led to roughly a dozen overdoses in recent days.

Police also believe the heroin is linked to the death of a woman on Sunday, but say they’re waiting for confirmation from the coroner to be sure.

Drug users are urged to be extremely cautious and not consume heroin alone. If possible, they should go to the supervised injection clinic Insite, which is staffed by medical personnel who can intervene in the event of an overdose, police said.

Those who see someone who appears to be in medical distress should call 9-1-1. Drug users who have done heroin and don’t feel well should seek help immediately.