Cory Monteith did NOT die from a new strain of deadly heroin that has been going around the Vancouver area -- this according to the coroner.
A police dept. 40 miles from Vancouver had issued a release warning a "toxic' mixture of heroin and fentanyl has caused a spike in heroin ODs.
The coroner who did the autopsy on Cory tells TMZ ... NO FENTANYL was found in Cory's system.
We're hearing the likely scenario is that Cory had not used heroin since entering rehab in April, and he may have gone back to the same dose he had learned to tolerate when he was using, but because his body was clean it couldn't handle the shock.