Four more ready-made sandwich brands have been added to a massive voluntary meat recall in connection with a deadly listeriosis outbreak across the country, the Canadian Food Inspection Agency said.

In a statement released early Tuesday, the CFIA said the Alberton, P.E.I.-based Atlantic Prepared Foods Ltd. is recalling its Irving, Sub Delicious and Needs brand sandwiches.

The products are sold in New Brunswick, Prince Edward Island and Nova Scotia.

There have been no reported illnesses associated with the consumption of these sandwiches, but they contain some of the meat products from the Maple Leaf Foods plant in Toronto that have already been recalled, the CFIA said.

Metro Ontario Inc. also pulled some of its Fresh 2 Go sandwiches from A & P and Dominion stores for the same reason, the CFIA said.

Over the weekend, the Toronto plant was confirmed as being involved in the outbreak of the food-borne illness, caused by the bacterium Listeria monocytogenes. On Monday, Maple Leaf upgraded a precautionary recall of 23 of its products, issued last week, to all 220 packaged meats from the plant.

29 confirmed cases, 15 deaths

On Tuesday, the company said it was again delaying the opening of the Toronto facility.

There are now 29 confirmed cases of listeriosis, up from 21, the Public Health Agency of Canada said Tuesday afternoon.

Of the 29, there are 15 confirmed deaths, mostly in Ontario but also one each in B.C., Saskatchewan and Quebec, the agency said. The listeria strain was the underlying or contributing factor in six of those 15 fatalities while the deaths of the other nine patients, who had the bacterium in their system, are still under investigation to determine the exact cause, the agency said.

Another 30 medical cases — in Alberta, Ontario and Quebec — are being examined for possible ties to the outbreak.

Food safety rules need 'revamp': Harper

Also Tuesday, Prime Minister Stephen Harper stressed the seriousness of the outbreak.

"This is a terrible development and I want to express my condolences to the families who have been affected," he said in Ottawa.

"I think all of us, and obviously I include my own family in this, we expect that when we shop that the things we buy or that we eat are going to be safe."

Harper cited increased resources and inspectors in the last federal budget as examples of how the government realizes it is necessary to "reform and revamp" Canada's food and product inspection processes after "some years of neglect."

"All members of government have been on top of this," Harper said.

"Obviously, we want to make sure that the companies maintain their responsibilities and that we fully review all the facts here, and understand what went wrong and how it can be prevented from happening in the future."

A secret cabinet document leaked last month suggested the Conservatives wanted to hand over inspection duties to industry.

In an interview with CBC's Dianne Buckner on Tuesday, Health Minister Tony Clement did not reveal the Conservatives' future plans for food inspection reform, instead echoing Harper's assertion that the government has already started making changes.

"Government policy was to hire 200 more inspectors, that's what we've done since we achieved power in January '06," he said from the U.S. Democratic National Convention in Denver, Colo.

"When it comes to health and safety, you can't scrimp and save; you've got to do your job on behalf of Canadians and that's what we're doing."

While critics have questioned Clement's presence in Denver in the wake of the listeriosis outbreak, Agriculture Minister Gerry Ritz, who is responsible for the CFIA, immediately returned to Ottawa from his Saskatchewan riding to manage the crisis.

Clement told Buckner it was important he attend the DNC as "we've got a lot of environmental issues with the United States, a lot of energy issues with the United States, and so part of my role here is to protect and defend Canadian interests."

He will return to Canada for a cabinet meeting on Wednesday, he said.

Contamination source may never be found

Symptoms of listeriosis — which include high fever, severe headache, neck stiffness and nausea — occur up to 70 days after consuming contaminated food, though the average incubation period is 30 days, the federal food agency said.

People most at risk include newborns, the elderly, pregnant women and people with weakened immune systems, public health officials said. People should wash produce and avoid unpasteurized milk and dairy products, the CFIA advised.

Public health and company officials said the source of the contamination may never be found since listeria is widespread and commonly found in the environment, such as in soil and in water.

Maple Leaf Foods estimates the recall will directly cost the company at least $20 million, with further losses expected due to lost sales and advertising to rebuild its image.

With files from the Canadian Press