Canadian prison guards were stunned to discover a pigeon carrying a "backpack" containing prohibited substances in the yard of a prison in British Columbia, the Canadian Broadcasting Corporation (CBC) reported Friday.

Guards were in a fenced area used for social and recreation for prisoners when one officer spotted a gray bird with something attached to its back.

"From my understanding, it was tied to it in a similar fashion as like a little backpack," said John Randle, a president of the Union of Canadian Correctional Officers, Pacific Region.

The guards investigated but it took "a lengthy period of time" to catch the culprit.

"They had to corner it," Randle said. "You can imagine how that would look, trying to catch a pigeon."

The backpack was found to contain 30 grams (1.06 ounces) of the highly addictive crystal meth drug. Short for crystal methamphetamine, it is an illegal and powerful street drug that at first creates a false sense of happiness in the user before continued use begins to destroy the body.

"It's definitely scary with the fact that it was crystal meth that was found on the bird because that causes a whole lot of problems," Randle said.

Homing pigeons had been employed previously to carry various items into prisons, but drones replaced the birds – last month a drone dropped a firearm into Canada's Mission penal institution.

But, because guards are on the lookout for drones, the pigeon appears to have staged a comeback.

"We've been focusing so much on drone interdiction ... now we have to look at, I guess, pigeons again," queried Randle.

The drug-carrying pigeon, while guilty, was released unharmed and happily sent on its merry way.