More prepared food products are being recalled in response to the nationwide listeriosis outbreak spawned by North York's Maple Leaf Foods.

Consumers are being advised to avoid cooked ham and salami sandwiches sold in Ontario by Sobey's, Foodland and IGA with a packed or best before date of Aug. 24.

Kirkland-brand croissant and meat-and-cheese-platters sold at Costco with a best before date up to Aug. 29 have also been added to the list, the latest in the string of recalled products containing tainted meat produced at the Maple Leaf plant.

On Wednesday, Maple Leaf Foods president Michael McCain made a statement taking full responsibility for the outbreak, brushing aside suggestions that federal or provincial food policies are to blame.

"It was our best efforts that failed -- not the regulators, the Canadian Food Inspection Agency," he said.

McCain also said the root cause of the listeria outbreak may never be known because the bacterium is so widespread. 

The Bartor Road plant will remain closed until the company is certain it can reopen under safe conditions.

Agriculture Minister Gerry Ritz says he's not blaming the plant's inspectors for the outbreak.

"I have no doubt that the plant will reopen," he says. "Having been subject to three or four chemical washdowns, there's very little chance there's any listeria there at all."

However, it would be possible for listeria to resurface in a very short time afterwards even after everything is declared "all-clear" at the plant, he says.

So far, eight deaths in Ontario and 15 across the country have been directly linked to the outbreak. Another 29 cases of listeriosis are confirmed across Canada, while 36 more are deemed "suspect."

More cases are expected to surface as listeriosis has a lengthy incubation period.

Two local law firms have joined the list of companies launching class-action lawsuits against Maple Leaf Foods. Both firms are advising consumers who may have eaten tainted meat to seek medical attention and have blood tests to look for signs of listeriosis. 

They also say not to throw out or return any contaminated products, and to keep them as evidence. Receipts and details of the purchase should also be saved.