At least 61 people in seven states have been made sick in an outbreak of Cyclospora linked to McDonald’s salads, federal health officials said Friday.

The fast-food chain has stopped selling the salads at 3,000 of its outlets, but more people may become sick, the Food and Drug Administration and Centers for Disease Control and Prevention said.

Salads at McDonald’s restaurants in at least 14 states may have been contaminated, the CDC and FDA said.

“We understand how important it is to quickly identify the cause of this foodborne outbreak to help reduce additional illness and we’re working closely with our colleagues at CDC and state partners to get more answers,” FDA commissioner Dr. Scott Gottlieb said in a statement.

“It’s early in the investigation, but we are taking steps now to help ensure consumers know about the potentially contaminated product so that they can better protect themselves or seek treatment, especially if they have signs or symptoms of a Cyclospora infection.”

Cyclospora is a fairly unusual parasite and it’s not easily removed by washing produce. Doctors may not be on the lookout for it as a cause of food poisoning, the FDA said.

It rarely kills, the CDC said.

“Most people infected with Cyclospora develop diarrhea, with frequent, sometimes explosive, bowel movements. Other common symptoms include loss of appetite, weight loss, stomach cramps/pain, bloating, increased gas, nausea, and fatigue,” the FDA said.

Symptoms may go away and come back.

“As part of this emerging investigation, the FDA is actively working with McDonald’s to identify the common ingredients in the salads identified by those who became sick and to trace back those ingredients through the supply chain,” the FDA said.

Cases have been reported in Iowa, Illinois, Minnesota, Missouri, Nebraska, South Dakota and Wisconsin, the FDA said.

But contaminated salads may have been sold in 3,000 outlets in 14 states, including Indiana, Michigan, Ohio, West Virginia, Kentucky, North Dakota and Montana.

“At this time, FDA has no evidence to connect this Cyclospora outbreak to those associated with Del Monte vegetable trays,” the agency said.

That outbreak has sickened 227 people in four states; Iowa, Minnesota, Wisconsin and Michigan. Del Monte withdrew the trays from sale in June.

“Past cyclosporiasis outbreaks in the U.S. have been linked to raspberries, basil, cilantro, snow peas and mesclun lettuce,” the FDA aid.

“Although it’s unknown exactly how food and water become infected with Cyclospora, people should be aware that rinsing or washing food is not likely to remove it.”

Foodborne illnesses are very common in the U.S. The CDC estimates that each year 48 million people get sick contaminated food, 128,000 are hospitalized, and 3,000 die. Bacteria, viruses and parasites can all cause foodborne illnesses.

This past spring, an outbreak of E. coli traced to romaine lettuce made more than 200 people sick and killed five.