A Saskatchewan senior who contracted listeriosis in the outbreak linked to Maple Leaf Foods has died, but health officials are not confirming that the bacteria caused her death.

The woman, who was in her late 70s, was a patient at a long-term care facility near Saskatoon.

She contacted the bacteria in July and died on Sunday, but health officials say she has been in and out of hospital with various health problems.

An investigation is underway to determine the exact cause of death.

Currently, at least 12 people infected with Listeria traced back to a Maple Leaf Foods plant in Ontario have died, although the bacteria is believed to have only caused -- or been a strong factor in -- six of those deaths.

More sandwiches pulled

Four more ready-made sandwich brands have been pulled from shelves following the massive recall of Maple Leaf Foods meat products.

In its first statement early Tuesday, the Canadian Food Inspection Agency (CFIA) said Metro Ontario Incorporated is warning the public not to eat its Fresh 2 Go turkey sandwiches.

The sandwiches, which contain the ready-to-eat deli meat products recalled by Maple Leaf Foods, were sold in A & P and Dominion stores in Ontario.

In a second statement, CFIA said Prepared Foods Limited has issued a warning about not consuming the Irving, Sub Delicious, and Needs brand sandwiches.

The sandwiches, which also contain Maple Leaf meat products, were sold in New Brunswick, Nova Scotia, and Prince Edward Island.

Maple Leaf issued a limited recall after Listeria bacteria was found on some of the products produced at one of its Toronto plants.

The company then recalled all meat products that were manufactured at its Toronto facility after three people died in Ontario, and one in British Columbia.

The expanded list -- described as precautionary by Maple Leaf -- now includes up to 220 products.

"There are inspectors all over the country as well as public health officials visiting establishments, restaurants and institutions to ensure this product is removed from the marketplace," CFIA spokesman Garfield Balsom told CTV's Canada AM on Tuesday.

CFIA officials and Maple Leaf executives say more testing is need to determine if the tainted meat directly contributed to any of the deaths.

"That would be an investigation by the Public Health Agency of Canada and the local health units," Balsom told The Canadian Press. "They do the food history, so they would make the linkages."

The disease has an incubation period of up to 90 days, meaning there could be more cases in the coming weeks.

Harper speaks

At an Ottawa news conference announcing a $100-million expenditure on Arctic seabed mapping, Prime Minister Stephen Harper told reporters on Tuesday that Canadians have a right to expect safe food.

"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," he said.

"This is a serious concern. That's why I indicated ... that it's necessary to reform and revamp our food and product inspection regimes."

Harper defended the presence of Health Minister Tony Clement at the U.S. Democratic National Convention in Denver, saying primary responsibility lies with the Agriculture and Food department.

"I think all members of the government has been on top of this," Harper said, adding he thinks the government has handled the crisis properly.

"I think we all feel tremendously for those who have been affected by this terrible development and I want to express ... my condolences to those families that have been affected."

Clement later told Newsnet from that he is in constant communication with Ottawa on the outbreak file and will be returning Wednesday for a cabinet meeting.

Lawsuit

Meanwhile, a Montreal lawyer who specializes in class-action lawsuits has launched legal action against Maple Leaf Foods.

Tony Merchant, of Merchant Law Group, said the suit will represent three classes of people -- those who have become sick after ingesting the food, those who have suffered a financial loss for having to throw meat out and those who are suffering from mental distress because of the outbreak.

"All sorts of people have eaten the meats and have the reasonable expectation that they may be endangered," said Merchant. "So, for the next 90 days, they're not even going to know if they have a problem.

"We believe that in this kind of an instance there may be millions of people who are entitled to compensation."

The suit is being launched in four provinces -- Ontario, Quebec, Manitoba and Saskatchewan.

Juanita Melvin, a plaintiff in the Maple Leaf lawsuit, got sick after eating one of the tainted products.

"I wasn't sure why I was sick and then I heard about the outbreak," Melvin told CTV's Canada AM on Tuesday from Quebec. "I went into a panic because in 1981 I lost my son because of the same bacteria."

Merchant said it could take months before a judge approves the cases and years before the complainants receive compensation.

"We'll find out whether Maple Leaf handled the recall properly and we'll find out whether they knew about the problems and reacted early enough," said Merchant.

Anyone wishing for more information from the company can call their consumer affairs hotline at 1-800-568-5801.

For more information online about the recalled products click here.

With files from The Canadian Press