Officials are issuing warnings after 67 people across the U.S. have been infected with E. coli linked to certain romaine lettuce, according to the U.S. Centers for Disease Control and Prevention.

The CDC advised people not to eat, purchase, serve or sell romaine lettuce that was grown in Salinas, California, over fears of possible E. coli contamination, according to a statement from the federal agency Tuesday.

The warning includes all types of romaine lettuce grown in the area, including whole heads of romaine, organic romaine, hearts of romaine and romaine in salad wraps.

The public should also stay away from packages of pre-cut lettuce and salad mixes that contain any romaine, according to the CDC.

Of those who have been infected with the outbreak strain of E. coli, 39 people have been hospitalized and six have developed hemolytic uremic syndrome, a type of kidney failure, the CDC said.

Wisconsin has reported the most ill people, with a total of 21.

So far, 18 other states — Arizona, California, Colorado, Idaho, Illinois, Maryland, Michigan, Minnesota, Montana, Nebraska, New Jersey, New Mexico, Ohio, Oregon, Pennsylvania, Texas, Virginia and Washington — have also reported people infected.

No deaths have been reported yet, according to the CDC.

Lab tests are said to have indicated that it is romaine lettuce from Salinas that’s making people sick. People can check to see where their lettuce comes from by looking for a label that shows where it’s grown. If the label either says “grown in Salinas” or does not say where it was grown, the CDC advised to throw it out and not eat it.

Most people infected with that strain of E. coli can experience diarrhea, which is often bloody, and vomiting. Many of those infected recover within a week, but, in rare cases, a person can develop a severe infection.