Michael McCain, CEO of Maple Leaf Foods, says that an investigation revealed that the most likely source of the Listeriosis outbreak was an accumulation of bacteria "deep inside" the components of two identical slicing machines.
The determination came after the machines were disassembled, McCain said at a Friday evening news conference.
He said that the machines' regular cleaning and maintenance went beyond the manufacturer's guidelines, but they were not disassembled under normal protocol.
He stressed that the machines are the "most likely" cause of the Listeria outbreak, but an "absolute determination is impossible" because of the bacteria's pervasiveness.
"When (the experts) complete their investigation the best they can do is advise what their best judgment is and they feel quite strongly about that judgment," McCain said.
"In their best judgment, this is the most likely cause."
McCain said the plant has since gone through four complete cleaning cycles under the guidance of external microbiologists and other experts.
He said the slicing equipment was torn down, deep cleaned four times, tested multiple times and then reassembled.
McCain said then when the plant starts back up no product will be released until the Canadian Food Inspection Agency is "fully satisfied" that all protocols are effective.
The investigation shut down the entire plant and 220 products produced there were recalled, at an estimated cost of $20 million.
There have been 13 deaths connected to the outbreak that has been linked to the Maple Leaf Foods plant in Toronto. 38 cased of listeriosis have been confirmed and another 20 are suspected.
McCain had previously issued an apology on behalf of his company in television and print ads released in August.
