OTTAWA, Ontario – Canadian officials have confirmed that an outbreak of listeriosis which has killed at least four people has been traced back to processed meats produced at a Maple Leaf Consumer Foods plant.

The Canadian Food Inspection Agency (CFIA) and the Public Health Agency of Canada (PHAC) have been testing samples of recalled meat for the past week to determine the source of a fatal outbreak of listeriosis, caused by Listeria monocytogenes.

On Saturday, the PHAC raised to 21 the number of cases of the outbreak that have been confirmed so far in four provinces. The agency said in a statement that 16 of the cases were found in Ontario, three in British Columbia, and one each in Saskatchewan and in Quebec.

Officials were working to confirm if a fifth case in Ontario is also linked to the outbreak, though reports were saying it was likely.

Authorities did confirmed that the outbreak has been traced to a Toronto meat-processing facility

Canadian Agriculture Minister Gerry Ritz and public health officials announced on Saturday night that genetic testing results from three samples of the recalled products show at least two tested positive for the outbreak strain of Listeria. The results are "highly significant" and show the investigation is "on the right path," the PHAC said in a statement.

Maple Leaf is recalling all sliced deli meat and other products from the Toronto facility "as a precautionary measure," the company reportedly said.

Sources: CanWest News Service, Associated Press