ATLANTA – A salmonella outbreak potentially linked to produce has sickened at least 172 people in 18 states, including Massachusetts, Rhode Island and Maine, health officials said Monday.

Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention, said Monday evening that state officials noted a cluster of about seven cases of salmonella several days ago. All of the cases were reported in southern Maine, she said.

“We had the feeling they might be part of a larger outbreak,” she said. Several children were affected, she said, but there were no hospitalizations. Some evidence pointed to consumption of raw fruits or vegetables.

Health officials think the bacteria may have spread through some form of produce – the list of suspects includes tomatoes. But the illnesses have not been tied to any specific product, chain, restaurants or supermarkets.

No one has died in the outbreak, which stems from a common form of salmonella bacteria. Eleven people have been hospitalized, health officials said.

“We’re very early in the investigation,” said Dave Daigle, a spokesman for the U.S. Centers for Disease Control and Prevention.

The CDC first detected the outbreak two weeks ago through a national computer lab system that looks for patterns and matches in reports of food-borne illness. The U.S. Food and Drug Administration has joined the investigation and will try to help trace the outbreak to its origin.

Most of the cases are in adults, and more than 60 percent are women, said Dr. Chris Braden, a CDC epidemiologist investigating the outbreak.

In addition to Maine, the states involved are Arkansas, Connecticut, Georgia, Indiana, Kentucky, Massachusetts, Michigan, Minnesota, North Carolina, New Hampshire, Ohio, Pennsylvania, Rhode Island, Tennessee, Virginia, Vermont and Wisconsin.

Salmonella infections are rarely fatal. Symptoms typically include diarrhea, nausea, vomiting, abdominal cramps, fever and headache.

There are about 2,500 types of salmonella. The type in this outbreak – Salmonella typhimurium – is one of the most common, Braden said.

People can catch the infection from many different sources, including water, soil, insects, factory surfaces, kitchen surfaces, animal feces, and raw meats, poultry and seafoods.

Outbreaks of food-borne illness have repeatedly made headlines this year. Certain brands of packaged spinach, lettuce, carrot juice, beef and unpasteurized milk recently were recalled after they were found to be tainted with illness-causing bacteria.

The most serious outbreak, first reported in September, involved spinach tainted with E. coli bacteria that killed three people and sickened more than 200.

Health officials estimate that more than 1.4 million cases of salmonellosis occur in the U.S. each year. About 1.3 million of those cases come from food, Braden said.

At the Maine CDC on Monday, Mills stressed the importance of practicing good “kitchen hygiene”: washing fruits and vegetables in cool water; disinfecting sponges, counters and other surfaces; washing knives and cutting boards used for preparing raw meat in hot soapy water before using them for produce; and washing hands frequently before, during and after preparing foods.

“It is important to ensure the safety of our food supply,” she said. “But no matter where we get our food, it’s never sterile.”

Mills said the Maine CDC would step up efforts beginning Tuesday to track the source of the contamination.