An advisory has been issued that beer sold in Toronto and Kamloops, B.C. may have been tampered with.

Six bottles of Stella Artois beer are believed to have been filled with concentrated alcohol, the Canadian Food Inspection Agency said in a consumer advisory published Thursday.

The 330 millilitre bottles have a best before of date of November 2005 or December 2005, and production codes of L32343T and L35243G.

But the CFIA said new labels seem to have been glued on top of the original labels on the neck of the bottles.

"These suspected tampering incidents occurred with beer sold at restaurants and bars in Toronto, Ontario and Kamloops, British Columbia," the advisory states.

"There are no reported incidents involving products purchased at beer or liquor stores. Stella Artois cans and draft beer are not affected.

Garfield Balsom of the CFIA told The Canadian Press that none of the bar and restaurant patrons who bought the affected products became sick, and that most tasted the high concentration alcohol and knew immediately that something was wrong.

The CFIA advisory said there had been some reported cases of vomiting associated with the consumption of the products.

Those who consume Stella Artois are being advised to check bottles for the best before dates and production codes, and for bottles that appear to have neck labels glued on top of each other.

Suspicious products should not be consumed.

Police are investigating the alleged tampering, and have the cooperation of Labatt Breweries of Canada and the CFIA.

Consumers with information regarding this suspected tampering should contact their local police department.