The Associated Press reports that cattle ranchers have been working to prevent fecal contamination in the Salinas Valley spinach and lettuce fields.

Ranchers were taking steps to keep livestock droppings from infecting produce long before the recent outbreak. These include designating watering holes for cattle so they don’t drink from creeks that flow through farms and creating “buffer zones” that keep the animals away from water that could later be used to irrigate crops.

The evidence so far indicates the spinach farmer, who also has not been identified, didn’t adhere to voluntary guidelines for vegetables meant to be consumed raw, said Kevin Reilly, deputy director of prevention services for the California Department of Health Services.

The San Jose Mercury News also reported that federal, state, and local investigators spent time Friday looking into one particular ranch near the spinach fields that may have been the source of the E. coli contamination.