Fentanyl's deadly reach is extending behind the bars of Canada's federal penitentiaries.

Just as the potent synthetic opioid first hit the streets in Western Canada a few years ago, the director general of security for the Correctional Service of Canada, Nick Fabiano, said he's seeing a similar albeit smaller pattern inside prisons.

"Over the last three years we've been able to identify that we've had 27 overdoses which have been linked in some way to fentanyl, and unfortunately we've also had six deaths in the last three years that have been linked to fentanyl," Fabiano told CBC News.

"We are currently investigating a couple of other deaths where we suspect that it could be fentanyl, but we haven't been able to confirm that yet."

As fentanyl is often disguised as other another kind of less-potent opioid, such as oxycodone, Fabiano said inmates sometimes don't know what they're taking. That, and the fact that just a grain of fentanyl can kill someone, "makes it a more dangerous drug than we've experienced in the past," he said.

The correctional service has responded by conducting awareness campaigns for inmates and offering programs to those who want to reduce their dependence on drugs. In mid-September, the service distributed Narcan — a nasal spray that can stop opioid overdoses — to correctional officers inside penitentiaries. Fabiano said it has already been used once.

All the while, Fabiano said, the correctional service has continued to try to stop drugs from getting inside through the use of ion scanners and drug detector dogs. When officials suspect fentanyl is already inside, Fabiano said, institutions have locked down penitentiaries and conducted exceptional searches.

Howard Sapers, Canada's correctional investigator, said there's no such thing as a drug-free prison. Yet he encourages the correctional service to employ a more hands-on approach to drug detection.

"That means being more present in the institutions, working with the inmate populations instead of just relying on static security things like ion scanners and drug detector dogs," Sapers said.