The Alberta plant at the centre of an E. coli scare and massive beef recall is being allowed to resume limited operations under tougher food testing rules.

But the Canadian Food Inspection Agency says no products will leave the XL Foods meat packer in Brooks until the agency is satisfied it is safe to do so.

"Beginning today XL Foods will be permitted to resume limited in-house cutting and further processing under strict enhanced oversight," Harpreet Kochhar, executive director for the agency's western operations, said Thursday.

"This will allow the CFIA to review in a controlled manner the company's improvements made to all previously addressed deficiencies."

The plant was shut down Sept. 27 during an ever-expanding recall of its beef products across Canada and more than 20 other countries. It hasn't been allowed to ship meat to its biggest market, the United States, for four weeks. The restrictions have led to lower cattle prices and a backlog of thousands of slaughter-ready animals in feedlots and ranches.

Kochhar said the plant has been cleaned and sanitized, and issues around condensation, drainage and ice buildup have also been addressed.

Workers will begin processing, under the scrutiny of more inspectors, 5,100 beef carcasses already inside the plant. No new animals will be slaughtered.

The carcasses have been tested for E. coli and are 99 per cent free of the bacteria, Kochhar said.

The main focus will be on more stringent E. coli control measures that have been imposed since a strain of the bacteria made 12 people sick in four provinces. There will be more tests of meat samples and increased monitoring of sanitation and hygiene.

"Meat from these carcasses will remain under CFIA detention," he said. "Products will not be allowed to leave the premises until the CFIA has confirmed in writing to the minister of agriculture and agri-food that the plant controls are effectively and consistently managing E. coli risks.

"The CFIA will immediately suspend operations if inspectors note any concerns with the facility's food safety controls."

Brian Nilsson, co-CEO of the company, said the tougher testing rules will allow XL Foods to identify meat at risk of E. coli and make sure it does not leave the plant.

"Our goal is to make sure it never happens again," Nilsson said in a release, adding that he apologizes to all people affected by the beef recall.

"We are optimistic to take this first strong step in concert with the CFIA towards resuming production in the facility."

The XL Foods plant is the second-largest meat packer in the country behind Cargill, and slaughters and processes more than one-third of Canada's beef.

Richard Arsenault, director of meat programs at the agency, said the lessons learned at XL Foods will eventually be applied to other meat plants.

He suggested the CFIA will not lower enhanced food safety standards that are now in place at the Brooks facility. The goal is to eliminate E. coli as much as possible from meat.

"Our goal here is that this will not be something that we will have happen in the next three months, six months, or ever again," Arsenault said.

"Our staff are paying special attention at what is going on in that plant to verify that the new written procedures are being effectively implemented."

The union for workers at the packing house has said problems go deeper than that.

Doug O'Halloran told a news conference Wednesday that the pace of slaughter operations forces workers to take shortcuts around cleanliness and puts the health of beef-eating Canadians at risk.

O'Halloran, president of the United Food and Commercial Workers Local 401, said the processing line at XL Foods moves too quickly.

"You can replace all the aluminum, all the stainless steel you want at the plant, but if you don't give your workers the tools to perform the job properly, we're not going to solve this problem," he said.

Between 300 and 320 carcasses go by workers every hour and employees make between 3,000 and 4,000 cuts a shift. That has resulted in less time in which to make sure knives are sanitized after each cut, the union president said.

O'Halloran wants a public inquiry into the problems that led to the plant's shutdown.

Alberta Premier Alison Redford rejected his demand Thursday while in Red Deer, Alta., for her premier's dinner.

Redford said it's more important to learn from what happened at the XL Foods plant. She said the province needs to work with the federal agriculture minister, the CFIA and XL Foods to see what needs to be improved.

The CFIA said Thursday it has contacted the union and wants to hear its concerns. However, Arsenault said the pace of work at the plant is not a concern as long as food safety rules are followed.

Ranchers such as Ryan Thompson welcomed word that the plant has begun what the food agency called a "progressive restart." But he said many producers are still worried about what could happen to the facility, which can handle about 4,000 cattle a day.

Thompson said the family-owned company that owns XL Foods, Nilsson Bros. Inc., has lost millions of dollars because of the recall and plant closure. More than 2,000 workers have been kept on the payroll.

He said some producers worry that if the plant doesn't resume full operations soon and win back customers it may go out of business.

That would leave thousands of Canadian producers with little choice but to send their cattle to the Cargill plant, in High River, near Calgary, or ship live cattle to the U.S. for processing, which would reduce already slim profit margins.

"It has obviously cost them (XL Foods) tens of millions of dollars. Going forward, is there desire to continue in the business? Until the plant is running, producers will have that concern," said Thompson, whose ranch is near Minden, Sask.

"We don't like to send our live animals into the U.S. and then import beef back into Canada."

The E. coli bacteria was first discovered Sept. 3 in tests by U.S. officials on meat heading south of the border. The U.S. stopped accepting shipments of beef from XL 10 days later. A recall of ground beef was eventually issued Sept. 16 and has been expanded numerous time.

The announcement Thursday came as Canada's meat and poultry food safety inspection system is to be audited by the United States Department of Agriculture for the first time since 2009.

A trade association that represents Canada's largest meat-packing companies says the USDA audit is to begin Oct. 22, and is likely to include a visit to the XL Foods plant.

"They will look at a representative sample of establishments across the country," said Jim Laws, executive director of the Canadian Meat Council from Toronto.

"Because this particular facility (XL Foods) is delisted, it would be incredibly opportune to be there in person and see it themselves."

The CFIA has given no timeline for when the Brooks plant will be allowed to accept cattle again or sell its products across Canada and abroad.

"We will not be rushing this process as our primary goal is food safety."