New Jersey's top health official is describing a recent spate of E. coli sickness as "a serious outbreak," but says the threat seems to have passed.

At least three dozen people were stricken and apparently all the victims had eaten at Yum Brands Taco Bell restaurants.

"There has not been an outbreak since Nov. 29, so I think that whatever happened went through already," Health and Senior Services Commissioner Fred M. Jacobs said Monday.

E. coli is a bacteria that can cause severe stomach distress and is most often spread through contaminated food.

State medical officials in New Jersey and New York were working with the Centers for Disease Control and Prevention to try to pinpoint what caused the outbreak that sickened at least 22 people in New Jersey — two of them seriously — and more than a dozen on Long Island.

"We have to find the food they all had in common," said David Papi, director of health for Middlesex County.

Taco Bell, a subsidiary of Yum Brands Inc., closed one New Jersey restaurant — in South Plainfield — and four in New York's Suffolk County on Long Island to sanitize them and replace food ingredients, company president Greg Creed said Monday.

Taco Bell is "very concerned about the well-being of all those who have been affected by this incident," Creed said, adding that the company was working closely with health officials.

All of those who fell ill in New Jersey had eaten at Taco Bells between Nov. 17 and Nov. 28, authorities said. Two employees of the chain also tested positive for the bacteria, although they were not sickened.

All but four of the New Jersey victims are under 18, authorities said.

Five were in the hospital Monday, including a 10-year-old boy and a 5-year-old girl who were diagnosed with hemolytic uremic syndrome, which can permanently damage the kidneys, officials said. The boy was in serious condition, while the girl's status had improved to stable, said Stephanie Brown, the Middlesex County epidemiologist.

Nine of 11 people confirmed with E. coli in Suffolk County, Long Island, reported eating at Taco Bell restaurants between Nov. 20 and Nov. 25, said Dr. David G. Graham, the county's acting health commissioner. Three people in Nassau County also were suffering from the illness, officials said.

E. coli, or Escherichia coli, is a common and ordinarily harmless bacteria found in the feces of humans and livestock. However, certain strains can cause abdominal cramps, fever, bloody diarrhea, kidney failure, blindness and paralysis, even death.

Most E. coli infections are associated with undercooked meat. The bacteria also can be found on sprouts or leafy vegetables such as spinach.

Earlier this year, three people died and more than 200 fell ill from an outbreak that was traced to packaged spinach grown in California. The bacteria also can be passed from person to person if they do not thoroughly wash their hands after going to the bathroom.