Illinois’s DuPage County Health Department has allowed the Los Burritos Mexicanos restaurant at 1015 E. St. Charles Road in Lombard to reopen while the source a June E. coli outbreak remains a mystery. The Lombard restaurant was closed June 14, but allowed to reopen last week while local health officials continue to investigate the cause of the outbreak. Including both confirmed and likely cases, 31 people were sickened in the outbreak, according to Jason Gerwig, spokesman for the local health department. Several of the illnesses were serious enough to require hospitalization, but all have since been released. The confirmed illnesses were caused by Shiga toxin-producing E. coli bacteria, which cause symptoms ranging from serious diarrhea to kidney failure. County health officials cleared the Mexican restaurant’s re-opening after staff training and cleaning. All old food, including canned food, was destroyed. About a dozen restaurant employees went through specialized training on sanitation, cross-contamination, and food surface cleaning. The restaurant will be subject to additional inspections and monitoring by the health department. Gerwig said the cause of the outbreak might never be determined with any certainty. Marco Arteaga, the restaurant manager, said they were thrilled to be open again. Its two other locations, in Villa Park and St. Charles, were not impacted by the closure.