Ottawa police say cocaine seized this summer contained fentanyl, the first time they've confirmed the presence of the potentially deadly opioid mixed in other street drugs.

The cocaine sample, seized by a patrol officer in early July 2016, was sent to Health Canada for analysis and the results were returned last week, police said.

It is the first Health Canada certificate of analysis confirming fentanyl's presence in another street drug, police said.

Fentanyl is a synthetic opioid doctors prescribe to help patients manage chronic pain. It's estimated to be 80 times more powerful than morphine and hundreds of times more powerful than heroin, according to the U.S. Centers for Disease Control and Prevention.

Fentanyl has also been linked to an increase in overdoses across the country, and health agencies have warned it's commonly cut into other street drugs to make them more potent. An amount equivalent to two grains of salt can kill a healthy adult.

"As always, police and Ottawa Public Health are advising that the best way to avoid an unintended overdose is by not using illegally obtained substances," police said in a statement released Thursday.

"No amount of supervision can ensure a person's safety when they choose to use illegal drugs. That is even more so when there is no reliable way for the user or the supervisor to confirm what drug is actually being ingested," police said.

In August Health Canada put forth a proposal to ban six chemicals used in the production of fentanyl, following the lead of a bill with the same aim put before the Senate by current Senator and former Ottawa police chief Vern White.

The public comment period for that proposal ended earlier this month.