The Ontario College of Pharmacists has launched an investigation after fentanyl was found in a naloxone kit assembled at an undisclosed pharmacy somewhere in the province.

The powerful opioid was located in a kit that was given to a customer at a Shoppers Drug Mart on Monday.

Naxolone is used to reverse the effects of an opioid overdose.

The drug can be administered through injection or nasal spray and is available for free at participating Ontario pharmacies.

“The pharmacy is fully cooperating and we are confident that immediate action has been taken to begin to determine how this happened and how it could have been prevented,” Ontario College of Pharmacists Spkesperson Todd Leach told CP24 in a written statement. “We have not been made aware of any similar incidents occurring at other pharmacies.”

Leach said that the investigation into how fentanyl came to be included in a naloxone kit is ongoing and therefore no further information can be released.

A spokesperson for Loblaw Companies Limited, meanwhile, told CP24 that “human error” was to blame.

The spokesperson said that the company is “taking appropriate steps to reinforce professional and operational expectations and procedures” in order to prevent the situation from happening again.

“We share the view that this is a considerable error and one that absolutely should not have happened,” Catherine Thomas said. “Our local pharmacist-owner took immediate action to ensure consumer safety, visiting the customers to secure the product and provide the correct medication, and to offer a detailed apology.”

Naloxone works by temporarily removing the opioids from the receptor sites in the brain.