(CNN) -- The salad mix blamed for a cyclospora outbreak in Iowa and Nebraska came from Mexico and was eaten by diners at Red Lobster and Olive Garden restaurants, the U.S. Food and Drug Administration announced Friday.
The federal agency said its investigators traced the "illness clusters" to four restaurants, which spokeswoman Theresa Eisenman later identified to CNN as Red Lobster and Olive Garden locations. The probe didn't find indications that any bags of salad mix were sold at U.S. grocery stores.
The tainted salad mix came from Taylor Farms de Mexico, "a processor of foodservice salads," according to the FDA.
As of Thursday, there had been 146 cases of cyclospora inspections -- an intestinal illness tied to a rare type of parasite -- reported in Iowa, according to that state's public health department. There were 82 reported cases in Nebraska.
What's happening in those two states may be linked to 140 cyclospora cases in Texas, that state's department of health services said Friday. As of then, authorities had not singled out a common source for the Lone Star State's outbreak, which is largely centered in and around Dallas and Fort Worth.
The U.S. Centers of Disease Control and Prevention has been collaborating with health officials in numerous states since late June trying to pin down what's causing the spate of cyclospora.
People get the disease by eating food or drinking water that's been contaminated with feces with the parasite, according to the CDC.
The ailment -- which strike in places where cyclospora is common, like tropical or subtropical regions, but is occasionally seen in the United States as well -- causes symptoms such as diarrhea, weight loss and nausea that can last anywhere from a few days to more than a month.