SOUTH PLAINFIELD, New Jersey — Taco Bell ordered scallions removed from its 5,800 US restaurants yesterday after tests suggested they may be responsible for the E. coli outbreak that has sickened at least three dozen people in three states.The Mexican restaurant fast-food chain said preliminary testing by an independent lab found three samples of green onions appeared to have a dangerous strain of the bacteria.

“In an abundance of caution, we’ve decided to pull all green onions from our restaurants until we know conclusively whether they are the cause of the E. coli outbreak,” said Greg Creed, president of Irvine, California-based Taco Bell.

The company would not immediately identify the supplier of the scallions, so it was unclear whether contaminated green onions reached other restaurants or supermarkets.

Tainted green onions from Mexico were blamed for a 2003 outbreak of hepatitis A in western Pennsylvania that was also traced to a Mexican restaurant. Four people died and more than 600 people were sickened after eating the green onions at a Chi-Chi’s. California is the largest US supplier of green onions. But by December, as winter sets in, the vegetable is often imported from Mexico.

The Taco Bell chain, a subsidiary of Yum! Brands Inc., reopened restaurants linked to the outbreak on New York’s Long Island after the outlets were sanitised. And two of three New Jersey Taco Bells implicated have also reopened, with authorities awaiting test results on customers from the third place.

But the fast-food chain closed nine outlets in suburban Philadelphia after health officials reported four people falling ill from E. coli.

McLane Co., which distributes food to the region’s Taco Bells, said federal investigators planned to test green onions, regular onions, cilantro, tomatoes and lettuce from its southern New Jersey warehouse.

Nine people remained hospitalised, including an 11-year-old boy in stable condition with kidney damage. New Jersey’s health commissioner has said the most recent case of E. coli was reported November 29, so the danger of infection appears to have passed.

E. coli is found in the feces of humans and livestock. Most E. coli infections are associated with undercooked meat. The bacteria also can be found on sprouts or leafy vegetables such as spinach. The germs can be spread by people if they do not thoroughly wash their hands after using the bathroom.