State health officials are investigating a cluster of salmonella cases in the Twin Cities involving five children who tested positive for the bacteria, one of whom was hospitalized.

Minnesota Department of Health officials connected the case to unpasteurized milk after two families said their children drank it. The other three children also were infected with the Salmonella typhimurium bacteria, indicating that the cases came from the same source.

The children range in age from 3 months to 10 years old. Symptoms of the strain of salmonella in these cases include diarrhea, cramps and fever, and last between four and seven days. Children under 5, adults over 65, and people with compromised immune systems are particularly susceptible.

Pasteurization heats milk to the point of destroying bacteria or other pathogens. Unpasteurized milk, sometimes called raw milk, may contain germs because animals could carry infections that don't harm them but do harm humans, or because the milk is contaminated with poop, according to the Centers for Disease Control and Prevention (CDC).

"Even healthy animals can carry these germs and have them in their milk," Maria Bye, senior epidemiologist in the Health Department's zoonotic diseases unit, said in a statement. "Consuming any unpasteurized milk is risky, no matter how clean the operation from which it is purchased."

People can be sickened both by raw milk and by products made from it, like ice cream and soft cheeses, according to the CDC. The agency warns that people can become sick from raw milk products even if they have consumed them from the same source in the past without illness.

The CDC estimates there are some 1.35 million salmonella infections each year in the United States, mostly from food.

The Health Department is working to find the source of the milk that sickened these children, and asks anyone who became sick after drinking unpasteurized milk in late June or early July to fill out a confidential online survey or to email health.foodill@state.mn.us.