Of 57 confirmed cases nationally, at least 20 have occurred in Wisconsin, including one death, state and federal officials said. Wisconsin was the first state to identify the particular strain of E. coli involved.

Besides the Wisconsin cases, the outbreak has sickened people in Connecticut, Idaho, Indiana, Michigan, New Mexico, Ohio, Oregon, Utah and Washington, according to federal health officials.

Preliminary analysis suggests the same bug is responsible for the outbreak in all the states.

Some grocery store managers are clearing shelves of pre-washed packaged spinach, although there has been no official recall. Many grocers around the state have already responded to the FDA’s outbreak announcement by working to voluntarily remove products from their shelves and keep their customers informed on the reported E. coli outbreak. Other bagged vegetables, including prepackaged salads, apparently are not affected.

Health officials do not know of any link to a specific growing region, grower, brand or supplier at present.