TORONTO - A CANADIAN food manufacturer at the centre of a deadly bacteria outbreak that killed at least 17 people across the country said on Thursday that a new strain found in contaminated meat poses no risk to the public.

Maple Leaf Foods CEO Michael McCain told reporters at a press conference that four meat samples that were tainted with the listeriosis bacteria were produced at the same Toronto plant linked to the fatal outbreak.

The tainted meat never left the company's control and were not released to stores, the company said.

'We tested, we identified a positive, we quarantined the product and it never left our controls. Our programmes are working. There is zero risk,' Mr McCain said.

Maple Leaf Foods and the Canadian Food Inspection Agency released statements on late Wednesday night saying four samples out of thousands taken at Maple Leaf's Toronto facility had tested positive for the bacterium.

Mr McCain said he held a press conference on Thursday explaining the latest findings to help Canadians understand Listeria and the 'plant that has been under the microscope.'

Mr McCain, in an attempt to restore trust in one of Canada's oldest food companies, has repeatedly addressed the public since the crisis hit the food manufacturer in mid-August.

The plant was shut down then after lab tests discovered the contamination, which was later traced to slicing machines.

None of the products produced at the plant since it reopened Sept 17 have been sold yet, the company said.

The Canadian Food Inspection Agency (CFIA) and Health Canada have said they will conduct comprehensive assessments of the new findings over the coming days.

Product from the Toronto plant will be rigorously tested each day for six weeks, said the CFIA.

The inspection agency said that the company can resume broader production only when test results are negative and operating procedures are determined to be in compliance.

Mr McCain said that the new strain found at the plant earlier this week is different from the one linked to the deaths.

He also stressed that Listeria can never be completely eliminated from food plants because it is so prevalent in the environment.

Eradicating the bacteria from the food industry is an 'impossible' expectation, he said.

'(Listeria) is estimated to be present in 30 per cent of raw meat and five per cent of humans are estimated to be carriers of Listeria. So every day when new raw material arrives and employees arrive, it's safe to assume Listeria enters the plant,' said Mr McCain, who added that it's the company and the food inspector's job to 'seek, find and destroy' the bacteria.

Mr McCain said that according to the Canadian Food Directorate, one to 10 per cent of all ready-to-eat food contains Listeria, but it is benign to the vast majority of the population.

Listeria bacterium, a type of food poisoning that can cause fever, nausea, abdominal pain and diarrhoea, was found embedded deep inside the plant's slicing equipment used on processed meats including bologna, turkey, ham and other products.

Maple Leaf recalled hundreds of products after the outbreak. -- AP