The Colorado Department of Agriculture said all meat samples taken from multiple lots of fresh and frozen McDonald's-brand beef patties tested negative for E. coli.

The agency has also completed testing of the beef and does not plan to conduct further testing of new samples.

In a statement, McDonald's chief supply chain officer Cesar Pina said all contaminated products linked to the E.coli outbreak have been removed from the supply chain and are no longer used in all of the company's restaurants.

McDonald's will resume distribution of fresh ingredients for its Quarter Pounder product, which is expected to be available in all restaurants next week.

However, affected McDonald's restaurants will serve burgers without onions.

E. coli bacteria in beef are killed by proper cooking. Quarter Pounders are served with sliced ​​raw onions, which are also suspected to be a source of contamination.

McDonald's restaurants in 13 affected states had previously temporarily removed the Quarter Pounder from their menus, although other items, including other beef burgers, remained available.

The fast food chain said its top priority was to "serve customers safely" and that the affected ingredients "very likely" entered its supply chain.