The McDonald’s are putting it back on the menu of all their restaurants in the US famous Quarter Pounder burgerafter ruling out the possibility that his burgers were the source of it E. coli outbreak which caused the death of one person while tens of others fell ill.

The fast food giant announced that samples of its burgers tested by the Colorado Department of Agriculture (CDA) were negative for the bacteria.

The company added that no further tests will be carried out.

McDonald’s suspended sales of Quarter Pounders last week at about a fifth of its US restaurants following the outbreak.

“The problem appears to be with a specific ingredient, and we are confident that any contaminated product associated with this outbreak has been removed from our supply chain,” said McDonald’s head of catering in North America.

Earlier, the FDA pointed to chopped onions in Quarter Pounders as another possible source of the outbreak.

McDonald’s said it had stopped working with the supplier of the onions and had removed them from its supply chain.

“The 900 restaurants that received the chopped onions from the Taylor Farms facility in Colorado Springs will continue to sell Quarter Pounders without chopped onions,” McDonald’s said.

McDonald’s is facing lawsuits from many people who got sick.

The US Centers for Disease Control and Prevention (CDC) advised people who had eaten a Quarter Pounder and experienced symptoms such as diarrhea, fever and vomiting to see a doctor.

Symptoms can appear up to four days after eating contaminated food.

Most people will recover on their own within five to seven days, but some cases may require hospital treatment.

McDonald’s shares have lost more than 7.5% of their value since the CDC reported the outbreak last week.