It appears that cilantro contaminated by human waste is to blame for several years of intestinal illnesses among Americans, according to the Food and Drug Administration.

The FDA announced on Monday that it has identified the cause of hundreds of U.S. cases of cyclosporiasis after health officials found human feces and toilet paper in growing fields in the state of Puebla, Mexico. The administration will detain Mexican cilantro at the border from April to August and forbid products from Puebla from entering into the U.S. without inspections and certification, according to a partial import ban dated Monday by the agency.

Last August, the FDA and Texas authorities linked suppliers in Puebla to infected cilantro at four Texas restaurants. Monday’s announcement, however, confirms that the central Mexican state is the source of many more cases of the disease.

Several major U.S. restaurant companies confirmed to Bloomberg Business that the cilantro they use will not be affected by the ban. A spokesman for Chipotle Mexican Grill Inc. said that all of its cilantro comes from California. Yum! Brands Inc., which owns Taco Bell, is also reportedly not affected.

As NBC reported last month, cyclosporiasis is not spread through human-to-human contact, but rather, through a host, such as contaminated food. Cyclosporiasis is caused by cyclospora, a single-celled, microscopic parasite that attacks the small intestine. According to the CDC, a cyclosporiasis infection can last from a few days to more than a month. Symptoms may go away, only to return later, and it is common to feel very tired. Cyclospora usually causes diarrhea and frequent bowel movements.

Other common symptoms include loss of appetite, weight loss, stomach cramps, bloating, increased gas and nausea. Other symptoms include vomiting, body aches, headache, fever and other flu-like symptoms. Some people who are infected do not show any symptoms.