Three more children, one of them an infant, have been sickened by a dangerous strain of E. coli linked to consumption of raw milk or cheese from a Gibbon, Minn., dairy farm, state officials said Friday.

The new cases bring the number of outbreak victims to eight, from seven homes, mostly in Hennepin County. The Health Department revealed the outbreak of E. coli O157:H7 illnesses on May 26 and has urged people not to consume the Hartman Dairy Farm's unpasteurized products.

Two of the latest victims are school-age children who consumed products from the farm on May 26 and May 27, though officials don't think their families deliberately ignored health warnings. "They probably just didn't know about it," said Dr. Joni Scheftel, state public health veterinarian for the Health Department.

One of the children was hospitalized for three days but has been released, she said. No one sickened in the outbreak remains in the hospital, including a toddler who earlier was hospitalized with a life-threatening complication from the pathogen, officials said.

The infant who recently got sick didn't consume the dairy products, and apparently picked up the bug from a family member stricken earlier in the outbreak, officials said.

State Agriculture Department officials said Friday that an investigation of the dairy is still underway. So far, 28 environmental and animal samples from the farm have tested positive for harmful E. coli, including 26 with the same genetic signature of the pathogen found in the sick consumers, the Health Department said.

In a new development, the department said three manure samples from the dairy's milking area also genetically matched the illness strain.

Despite those findings, Hartmann can legally sell raw milk on the farm under a state law that permits occasional, on-farm sale of raw milk. Hartmann's customers have used an informal distribution system relying on drop points at some consumers' homes.

"We do not have cease-and-desist authority," said Heidi Kassenborg the Agriculture Department's director of dairy and food inspection, when asked why Hartmann's raw milk is still available.

Regulators have authority to order a dairy to correct unsanitary conditions, but that action can be challenged and doesn't immediately block on-farm sales of raw milk, said Nicole Neeser, the department's dairy inspection program manager.

Hartmann has questioned the scientific basis of the Health Department findings, noting that no harmful E. coli was detected in raw milk samples. When a reporter called the farm Friday, a man answered the phone but wouldn't identify himself and referred questions to Gary Wood, a spokesman.

Wood responded by e-mail that the government's case "is inconsistent with the common-sense conclusion that if there is no E. coli found in the milk it cannot be the source of anyone's illness."

Scheftel, of the Health Department, said it can be difficult to isolate such pathogens in food, but this case involves a rare strain of E. coli never before seen in Minnesota.

"The fact that it was very rare, it was found in the animals' environment and found in the people is extremely strong evidence," she said.

David Shaffer • 612-673-7090