(CBSNews.com) - A bagged salad mix is being investigated as a source of the cyclospora stomach bug outbreak that has caused hundreds of cases of diarrhea.
As of July 29, 372 people have developed a cyclospora infection, or cyclosporiasis, the Centers for Disease Control and Prevention announced Tuesday. Cases have been found in at least 16 states: Iowa, Texas, Nebraska, Florida, Wisconsin, Illinois, Georgia, Missouri, Arkansas, Connecticut, Kansas, Minnesota, New Jersey, New York, and Ohio.
The most cases -- 143 -- have been reported in Iowa. An investigation by the Iowa Department of Public Health has implicated a prepackaged salad mix as the source of the state's outbreak. Investigators determined that about 80 percent of the cases had been exposed to this same type of prepackaged salad mix.
Health officials have not revealed the brand or manufacturer of the mix, but have said it contains iceberg and romaine lettuce, carrots and red cabbage. The salad mix is no longer in Iowa's food supply chain, the health department said.
Federal health officials have yet to conclude this bagged salad is responsible for the nationwide outbreak,
"FDA will continue to work with its federal, state and local partners in the investigation to determine whether this conclusion applies to the increased number of cases of cyclosporiasis in other states," the agency said in a statement. "The goal will be to combine information collected from other affected states with that provided by the state health authorities in Iowa to identify a specific food item linked to the illnesses."
The FDA added it is following other leads as well. A seven-person team at the agency's headquarters is working to solve the outbreak.
"This is labor intensive and painstaking work, requiring the collection, review and analysis of hundreds and at times thousands of invoices and shipping documents," the FDA said.
Cyclosporiasis is caused by the parasite, cyclospora, found in contaminated food or drinking water.
Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University, previously told CBS This Morning Thursday that cyclospora is a "tenacious critter because it can produce a prolonged, watery, very uncomfortable diarrhea" in addition to other symptoms like cramping, bloating, gas, nausea and fatigue.
Iowa health officials said the diarrhea can last up to 57 days.
The Food and Drug Administration urges people to practice safe food handling and preparation, including washing hands, utensils and surfaces with hot, soapy water before and after handling foods.
© 2013 CBS Interactive Inc. All Rights Reserved.