Montana public health officials are investigating an outbreak of infections caused by Salmonella. The Cascade City-County Health Department in Great Falls is reporting that six students at Sacajawea and Valley View elementary schools have tested positive for the pathogen. A staff member at another school has also tested positive.

There is also a person with no connections to any school who has tested positive for the outbreak strain. The first patient was reported on Oct. 30.

The most recent person to become ill had symptom onset on Nov. 12, according to a news release from the health department. “The CCHD has been in contact with all confirmed individuals and is working with Great Falls Public Schools nursing staff and leadership to notify families, limit the spread, and identify potential sources of contamination,” according to the health department’s statement.

The source of the outbreak has not yet been confirmed, but officials are interviewing patients and their families about what foods they have consumed recently in hopes of finding a common exposure. The Montana Department of Public Health & Human Services is also investigating connections to other Salmonella cases in other Montana counties and states. About Salmonella infections Food contaminated with Salmonella bacteria does not usually look, smell, or taste spoiled.

Anyone can become sick with a Salmonella infection. Infants, children, seniors, and people with weakened immune systems are at higher risk of ser.