DENVER (KDVR) — Following a deadly E.coli outbreak tied to McDonald’s Quarter Pounders, the Colorado Department of Agriculture tested the chain's beef patties for the bacteria. On Oct. 22, the Colorado Department of Agriculture said its laboratories received multiple lots of McDonald's fresh and frozen patties from various Colorado locations that were associated with the deadly outbreak. Colorado resident files lawsuit against McDonald’s for E. coli outbreak The department's microbiology lab analyzed dozens of subsamples of the patties and said they were all negative for E.coli. The Colorado Department of Agriculture said it has completed its testing of the beef and does not anticipate receiving more samples. According to the department, the federal investigation into the outbreak has focused on the beef patties and onions. However, the department does not have information suggesting onions grown in Colorado were linked to the outbreak. McDonald's discusses further customer safety steps McDonald's held a briefing to discuss the results of the testing on Sunday afternoon. The fast food provider has removed all slivered onions linked to a Colorado Springs location from all McDonald's locations. The removal took place on Oct. 22, and will stop sourcing onions from the Taylor Farms location indefinitely. The company is also obtaining a new supply of fresh beef patties for the 900 stores that could be impacted by this outbreak, resuming sales of the Quarter Pounder in Colorado, Wyoming and Kansas, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma and Utah. The company noted in its briefing that due to the increased awareness of the outbreak, more people are likely to seek medical attention, growing the number of cases associated with this outbreak. The restaurant noted that the issue appears to be "contained to a particular ingredient and geography, and we remain very confident that any contaminated product related to this outbreak has been removed from our supply chain and is out of all McDonald’s restaurants." The fast-food giant said the bottom line is that its Quarter Pounders are safe, and the burger, without onions, will be rolled out to the affected restaurants on a rolling basis. The company also noted that other menu items using onions source the onions from different suppliers. Onions from California-based company linked to outbreak While Colorado onions were not linked to the outbreak, a California-based produce company was likely the source of the onions that had E.coli, according to officials. McDonald’s officials said that Taylor Farms, of Salinas, California, sent onions to one distribution facility. U.S. Foods, a major wholesaler to restaurants across the country, said Thursday that Taylor Farms had issued a recall this week for peeled whole and diced yellow onions for potential E. coli contamination, Taylor Farms also has a facility in Colorado, but it has not been linked to the investigation. However, the fast food company decided to stop sourcing from that location out of precaution and said other restaurants will likely move to stop selling onions sourced from that facility or will recall the onions. Taylor Farms said Friday it had preemptively recalled yellow onions sent to its customers from its Colorado facility and continues to work with the CDC and the FDA as they investigate. “It saddens us to see the illnesses and affected individuals and families,” from the outbreak, the family-owned company said. Taylor Farms notified its customers directly about the onion recall but did not tell the public about it, an FDA official said. Companies often issue press releases and the FDA sends public notifications for recalls, but they are not required. While it remains unclear if the recalled onions were the source of the outbreak, several other fast-food restaurants — including Taco Bell, Pizza Hut, KFC and Burger King — pulled onions from some menus in certain areas this week. Restaurant Brands International, which owns Burger King, said that 5% of its restaurants use whole onions distributed by Taylor Farms’ Colorado facility. They are washed, peeled and sliced by employees. Even though it wasn’t contacted by health officials and it had no indications of illness, Restaurant Brands said it asked the restaurants that received onions from the Colorado facility to get rid of them. At least 75 sickened from outbreak At last update on Friday, federal health officials said at least 75 people in 13 states have become sick following the outbreak. One person from Mesa County has died. McDonald’s E. coli outbreak: Why only the Quarter Pounder was linked Some people who got sick reported traveling to other states before their symptoms started. At least three people said they ate at McDonald’s during their travel. Illnesses were reported between Sept. 27 and Oct. 11. Symptoms of E. coli poisoning can occur quickly, within a day or two of eating contaminated food. They typically include fever, vomiting, diarrhea or bloody diarrhea and signs of dehydration — little or no peeing, increased thirst and dizziness. The infection is especially dangerous for children younger than 5, people who are elderly, pregnant or who have weakened immune systems. The Associated Press contributed to this report.