Health officials say that the steaks eaten by four people who are now sick with E. coli poisoning were processed at an XL Foods plant in Brooks.

However, they aren’t confirming that the factory is the real source of the bacteria and they don’t know how the meat could have been contaminated.

Alberta Health Service employees say the contamination may have occurred during a tenderizing process done at Costco, so they have asked the store to discontinue that procedure.

A massive recall of meat was triggered after E. coli was discovered in a container of meat headed to the U.S. a few weeks ago.

A report from Canadian Food Inspection Agency found that there were discrepancies with consistently reporting high levels of E. coli in the meat at the plant.

A union representative for the CFIA inspectors says that the problem really stems from the decision years ago to allow meat producers to be in charge of their own E. coli testing.

“They’re self-regulating, they do the sampling, they do the testing, they determine if the product is contaminated,” Fabian Murphy of the Agriculture Union says. “In this case, my understanding is the plant did do testing but it wasn’t picked up.”

The CFIA says the plant did not properly report the high levels of E. coli.

There is no clear reason why the plant did that.