Maple Leaf Foods products that have been recalled because of possible contamination with Listeria were found in at least two Montreal stores on Wednesday, as Prime Minister Stephen Harper vowed to have an independent investigation into the outbreak.

CTV Montreal found a box of Hygrade pepperoni sticks -- included in the recall list -- at a convenience store. The owner said his family had purchased the products from a supplier about two weeks ago, but he had not been told it should be taken off the shelves.

"We didn't get any report," he said. "We didn't get anything."

At another convenience store, CTV Montreal found Shopsys pepperoni sticks that had also been included in the recall list. Their product code had "97B" -- linking it to the Maple Leaf Foods plant in Ontario that has been linked to the outbreak.

A store spokesperson said he had purchased the product about three weeks ago. Maple Leaf Foods issued its first recall list around Aug. 19.

Jean-Louis Michaud, a spokesperson for the Canadian Food Inspection Agency, said stores and suppliers should have been notified about the recall list.

"We're concerned because every single retailer has been informed already. So we're looking at what has happened," he said.

There are roughly 30,000 convenience stores -- or "depanneurs" -- in Quebec.

Harper told reporters Wednesday he was "very troubled" by the deadly outbreak.

The prime minister told reporters, during a campaign-style stop in Windsor, Ont., that the investigation will aim to prevent a similar outbreak in the future.

The statement came on the same day the CFIA said an Ontario-based grower is recalling some of its mushrooms over Listeria-contamination fears.

Ravine Mushroom Farms Inc., of Woodbridge, Ont., is pulling its Fresh Obsessions-brand Ready to Serve pre-washed, sliced white mushrooms from store shelves in Ontario.

The mushrooms are sold in eight-ounce packages with the lot code R12398.

The code can be found ink jetted on the cellophane wrapper on the side of the package.

The CFIA said Wednesday there have been no reported illnesses associated with the consumption of the product.

The statement did not indicate any link between the mushroom recall and the nation-wide Listeriosis outbreak connected to a Maple Leaf Foods plant in Toronto.

The Public Health Agency of Canada says the number of confirmed deaths in which listeriosis was the underlying or contributing cause remains steady at 12.

On Tuesday, Dr. David Butler-Jones, Canada's chief public health officer, said the peak of the public's exposure to Listeria probably happened around the end of June.

With an incubation period ranging between three to 70 days, he said the number of new cases is likely to dwindle. Also, the number of suspected cases of listeriosis has dropped from 21 to 14.

Still, Maple Leaf Foods President Michael McCain said Wednesday his company is continuing to work on a comprehensive action plan to fix the situation.

"Candidly, I'm not going to allow that facility to open until I'm personally satisfied," he told CTV's Canada AM.

McCain said his long-range plan includes creating a position of chief food safety officer within his organization.

He said he's also going to assemble a "world-class team" of third-party experts to advise the company on the newest technologies to keep food safe.

Food contaminated with Listeria monocytogenes may not look or smell spoiled, warns the CFIA.

However, Listeriosis can cause high fever, severe headache, neck stiffness and nausea.

Pregnant women, the elderly and people with weak immune systems are particularly at risk. Infections during pregnancy can lead to premature delivery, infection of the newborn or stillbirth, says CFIA.

With files from CTV Montreal The Canadian Press