(Image source from: Mirror)

More than 500 McDonald's customers fell sick after a parasite typically found in human waste was found inside the fast food chain's salads.

The Food and Drug Administration (FDA) launched a probe after 507 people across 16 states reported sickness and diarrhea.

The unwanted component hidden within the lettuce is known to cause intestinal malady.

Symptoms typically begin after a week and include 'explosive' bowel movements.

On Wednesday, the FDA confirmed cyclospora was detected within the Fresh Express romaine lettuce and carrot mix that McDonald's use in their meals.

The ghastly situation initially came to light on May 20, according to the Centers for Disease Control (CDC) and Prevention.

The restaurant decided temporarily remove the salads at the 3,000 affected restaurants on July 13.

Connecticut, Florida, Iowa, Illinois, Indiana, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota, Tennessee, Virginia, Wisconsin and New York were all affected by the contaminated salads.

Cyclospora parasite can likewise cause weight loss, stomach cramps, nausea, body aches, and fever and in some cases, it can last as long as a few months.

The CDC's statement read: "Epidemiologic evidence indicates that salads purchased from McDonald's restaurants are one likely source of these infections."

"The investigation is ongoing, and FDA is working to determine the sources of the ingredients that were in common to the salads served at McDonald's."

On July 27, Fresh Express issued a callback for some lettuce that had been supplied to retail and institutional customers.

They as well reported that the carrots used in the mix were only sent to McDonald's locations.

McDonald's said: "The health and safety of our customers and the people who work in McDonald’s restaurants is always our top priority."

"The additional states identified by the FDA and CDC are among the same states where a week ago we proactively decided to remove our lettuce blend in impacted restaurants and replace it through a different supplier.

"McDonald's is committed to the highest standards of food safety and quality and we continue to cooperate and support regulatory and public health officials in their investigations."

"For those seeking additional information about Cyclospora, we encourage them to visit the CDC and FDA websites."

By Sowmya Sangam