Police officials in Vancouver, Canada have issued a red alert warning to drug users in the city about the potency of heroin on the local market following a spike in overdoses, including that of tragic actor Cory Monteith.

The Glee star died in his hotel room in Vancouver on Saturday (13Jul13) and autopsy and toxicology test results have confirmed the cause of death was an accidental overdose.

Now, a day after Monteith's remains were reportedly cremated, city lawmakers have raised the alarm on a dangerously potent toxic grade of the drug.

A police statement reads: "The Abbotsford police department has observed a concerning increase in the numbers of heroin overdoses in the community."

Officers claim they had detected the presence of fentanyl, which is used to treat cancer-related pain, in recent supplies of heroin, which causes increased potency.

The statement continues, "Our front line officers have spoken with many individuals who have reported being concerned about the potency of heroin that is currently being bought, sold and used."

It is not clear whether or nor police think the batch of heroin Monteith took was laced with fentanyl.