Cattle grazing next to or near romaine lettuce fields is “the most likely contributing factor associated with” E. coli outbreaks last fall, the Food and Drug Administration said in a report released Thursday.

The three outbreaks, traced to lettuce from the Salinas Valley, sickened 188 people.

The agency said it could not confirm definitively the “source or route(s) of contamination of the romaine fields.”

However, possible routes of contamination include “indirect transmission of fecal material from adjacent and nearby lands from water run-off, wind, animals or vehicles to the romaine fields, or to the agricultural water sources used to grow the romaine.”

FDA also said: “The number of cattle we observed on nearby lands during the 2019 investigations was far lower than the volume of what is considered a large concentrated animal feeding operation, offering a useful reminder that high-density animal operations are not the only factor to consider.”