U.S. health officials are investigating a Salmonella Infantis outbreak that is likely linked to raw flour. It's not clear what brand of flour is the culprit.

Investigators from the U.S. Centers for Disease Control and Prevention and Food and Drug Administration have identified 12 illnesses and three hospitalizations occurring across 11 states.

Reported illnesses started on Dec. 6 and continued through Feb. 13. Those sickened are mostly female and range from 12 to 81 years old.

The true number of people infected in this outbreak could be much higher than the number reported, since many people recover without medical treatment or don't get tested for Salmonella. It also takes three to four weeks to determine if a sick person is part of an outbreak, the health agency said.

So far, states with known illnesses include Oregon, California, Nebraska, Minnesota, Iowa, Missouri, Illinois, Ohio, Tennessee, Virginia and New York.

Among the seven people investigators interviewed, six reported eating raw dough or batter. Flour was the only common ingredient, and investigators are working hard to identify the brand.

To stay safe, don't eat or play with uncooked flour, dough or batter, the CDC cautions, noting any raw — or unbaked — flour can contain germs like Salmonella.

Health officials offered some other advice:

• Follow the recipe or package instructions for cooking or baking flour.
• Use the temperature and cooking time given in the recipe or instructions.
• Buy heat-treated flour to use in recipes for homemade playdough. Children can get sick from handling raw dough used for crafts or play clay.
• Use warm water and soap to wash your hands and any bowls, utensils and surfaces that touched raw flour.
• Keep raw flour, dough and batter separate from foods that won’t be cooked.
• Immediately call a health care provider if you or your child have diarrhea and a fever higher than 102°F, diarrhea for more than three days that is not improving, bloody diarrhea or so much vomiting that you cannot keep liquids down.

Also call the doctor if you have signs of dehydration, such as not peeing much, dry mouth and throat or feeling dizzy when standing up.

Symptoms of infection with Salmonella include diarrhea, fever, and stomach cramps. These typically start somewhere between six hours and six days after swallowing the bacteria.

Most people recover without treatment after four to seven days.

Children younger than 5 years, adults older than 65 and those with weakened immune systems may experience more severe illnesses that require medical treatment or hospitalization.