FLOYDS KNOBS, Ind. (AP) – An outbreak of E. coli has sickened at least 10 people, including seven schoolchildren, and officials have ruled out school cafeteria food as a source.

All the people infected last month are linked in some way to Galena Elementary School in Floyds Knobs, a southern Indiana town about 15 miles northwest of Louisville, Ky. Three of the cases are not students.

At least three of the cases appear to have been caused from exposure to a sick family member, the school district told parents in an online update Wednesday.

“This type of person-to-person transmission occurs when an ill person does not wash hands thoroughly after using the bathroom and may have been a contributing factor for illness transmission among the students at the school,” wrote Bill Briscoe, the district’s assistant to the superintendent for administration and operations.

Galena Elementary has remained open since the first infection on Sept. 21, and officials say it has been cleaned regularly.

“We’ve taken precautions,” Rarick said. “I’m a parent. I understand those concerns.”

In addition to the 10 confirmed cases this week, health officials were still waiting on lab results for some other suspected infections.

According to the CDC, the United States has about 73,000 cases of E. coli infection and 61 deaths each year. E. coli causes intestinal illness that generally clears up within a week for adults but can be deadly for the very young, the elderly and people with compromised immune systems. Symptoms can include severe stomach cramps, bloody diarrhea and, in extreme cases, kidney failure.