RACINE - City and state health officials suspect the cause of the mysterious illness that hit Racine Unified schools last week might be linked to flour tortillas served in district schools, state health officials said Friday.

State and city health officials continue to investigate the gastrointestinal illness that sickened more than 90 students and at least five teachers at three Racine middle schools.

Although lab results are pending, all three middle schools served the same lunch items, health officials said.

Interviews with students led health officials to suspect six-inch, soft flour tortillas served between Oct. 29 and 31.

"While we don't have a definitive link, we have a commonality," said Stephanie Marquis, spokeswoman for the state Department of Health and Family Services. "Although we don't have a laboratory confirmed test, the common source is six-inch flour tortillas."

Chicago-based Del Rey Tortilleria, Inc., produced the flour tortillas served at all three middle schools where students and teachers suffered from vomiting, stomach cramps and other symptoms, state health officials said.

Officials at the state hygiene lab found no evidence that an infectious agent caused the illness, said Marcia Fernholz, Racine's environmental health director.

Stool samples from sickened students tested negative for bacterial pathogens or norovirus, the most common causes of food-borne illness, Fernholz said.

FDA investigates

Food and Drug Administration officials from Minneapolis pulled several cases of Del Rey flour tortillas from Unified kitchens this week, said Dan Blimling, district manager for Chartwells, Unified's food service provider.

"What we have now is a focus on a different product. It's detective work. It's not fast and it's not glamorous," Blimling said. "There's a tendency to say, 'That's it.' We don't know that and we've got to be careful."

School district officials learned about the suspected cause in time to change Friday's menu at elementary schools, which included soft shell tacos.

"We knew there was a focus on the tortillas, so the tacos became nachos," Blimling said.

The Department of Public Instruction issued a warning to all schools in the state, advising them not to serve flour tortillas, as a precaution.

"We wanted to err on the side of caution, just in case," said DPI spokesman Patrick Gasper, "Tacos seem to be a staple on school lunch menus. Until we know more, we don't want people getting sick for no reason."

The case linked to the illness contained 40 packages and labeled Del Rey Flour Tortillas Number 6, according to health officials. The tortillas came in 12-ounce bags, 12 tortillas per package.

The company also sells tortillas in grocery stores.

No recall

The FDA had not ordered a recall of Del Rey products as of Friday, but continues to investigate.

A Del Rey general manager could not be reached for comment Friday, but Blanca Rojas, an employee, said Del Rey staff was cooperating with FDA officials during the investigation.

The company voluntarily recalled flour tortillas in January 2006 after the FDA linked their products to an illness outbreak among consumers who

complained of stomach pains, vomiting, diarrhea, nausea and headaches.

The reported symptoms typically occurred very soon after eating the flour tortillas and cleared up within one day, according to a company statement from that time.

The company's tortillas were linked to an illness outbreak in December 2005 that sickened 53 students and three staff members at five middle schools in Illinois, according to health officials.

The Illinois Department of Public Health, the Centers for Disease Control and the FDA investigated that outbreak. The illnesses occurred within 30 minutes of eating school lunch, which included soft tacos.

Health officials have drawn comparisons between Racine's illness outbreak and similar outbreaks throughout the country, at different times during the past 10 years.

Lab results following a 2003 outbreak in Massachusetts suggested elevated levels of two chemical additives used in the production of Del Rey tortillas - potassium bromate and calcium propionate. The levels were elevated compared to common industry practices, according to the CDC.

A recent smaller outbreak associated with flour tortillas occurred in September in Iowa, health officials said.

The FDA tested tortillas related to that outbreak, but results were still pending, health officials said.

"The important piece is that there are no long-term effects on the people who suffered from this, based on reports of similar incidents," said Jack Parker, Unified's interim superintendent.