WASHINGTON — Fresh cilantro from a Mexican city has been banned from coming into the U.S. after a government investigation found human feces and toilet paper in fields used to grow the green herb, the Food and Drug Administration said.

The FDA announced the partial ban on Monday after cilantro imported from the state of Puebla was linked to 2013 and 2014 outbreaks of stomach illnesses in the United States.

U.S. and Mexican health authorities investigated farms and packing houses in Puebla and found that some of the farms had no running water or toilet facilities.

The ban will affect only certain shipments of fresh cilantro from Puebla from April through August, corresponding to the timing of the outbreaks. The summer ban will continue in future years unless a company can prove to health authorities that its product is safe.