Federal health officials have linked four more states to an outbreak of a diarrhea-causing parasite. The update announced Friday expands the scope of the largest U.S. outbreak of cyclospora on record. Federal health agencies have been investigating the outbreak tied to shredded lettuce served at Taco Bell restaurants. Their tracing efforts now include Illinois, Kansas, Oklahoma, and Pennsylvania. Previously the agency’s investigation included five states: Indiana, Kentucky, Michigan, Ohio and West Virginia. Investigators are focused on produce supplier Taylor Farms and imports of lettuce from a location in Mexico.