The Mexican-style franchiser removed green onions from all 5,800 of its restaurants across the country Wednesday after tests indicated they could be to blame for an outbreak of E. coli that has sickened at least five dozen people in New Jersey, New York and Pennsylvania.

    "I have contacted company officials and asked that they voluntarily close all 15 of their establishments in Philadelphia until they are given approval by the health department," said Philadelphia interim health commissioner Carmen I. Paris in a statement.

    Taco Bell said preliminary testing by an independent lab found three samples of green onions that appeared to have a dangerous strain of the bacterium.

    Health officials claimed it as the largest E. coli outbreak to hit the Northeast in years. At least 65 people are now known to have been infected, nine of whom remained in hospitals, including an 11-year-old boy who was in stable condition with kidney damage.

    Tainted green onions from Mexico were blamed for an outbreak of hepatitis A in western Pennsylvania in 2003 that was traced to a Mexican restaurant. Four people died and more than 600 others were sickened after eating the green onions at a Chi-Chi¡¯s restaurant.

    The mystery arose Thursday, when a hospital in Middlesex County, N.J., notified the state Health Department of a confirmed case of E. coli. More incidents were reported on Long Island in New York, and the reports spread Tuesday to Pennsylvania.

    State health officials there told NBC News they had confirmed four patients, three of whom had eaten at separate Taco Bells in Montgomery County.

    "I started getting really sick," said Christina Swindell, a Taco Bell customer in New Jersey. "I started to feel nauseous and a lot of diarrhea.."

    Health officials said the number of reported cases could still rise, but the danger of new infections is likely to have passed.

    But Abby Greenberg, disease control director of the Nassau County (N.Y.) Health Department, said Wednesday that people who may have eaten at Taco Bells in the Northeast should still be alert to symptoms and seek treatment quickly if they appear.

    "The important public health message is anyone who is suffering from severe diarrhea, particularly bloody diarrhea typical of the severe E. coli 157 infection, to contact their physician immediately," she said.

    Taco Bell, a subsidiary of Yum! Brands Inc. based in Irvine, Calif., reopened restaurants linked to the outbreak on Long Island after the outlets were sanitized. And two of three New Jersey Taco Bells that were implicated had also reopened, with authorities awaiting test results on customers from the third location.

    Taco Bell said Tuesday that all the ingredients prepared at the 1,100 Taco Bells in the Northeast came from its distribution center in southern New Jersey, which is operated by McLane Food Service of Carrollton, Tex. McLane said federal investigators planned to test green onions, regular onions, cilantro, tomatoes and lettuce from the warehouse.

    (Agencies)