Earlier this month, St. Louis County Health Department officials announced that they will offer HIV tests at Normandy High School after a public health inspection determined that some of its students may have been at risk for HIV infection. On October 22, however, officials said that the estimated number of students who may have been exposed to the virus may be as high as 50, the St. Louis Dispatch reports.

“It could well be substantially below that,” said Craig LeFebvre, spokesman for the St. Louis County Department of Health. “Just because you’re exposed doesn’t mean you contracted the disease.”

According to the article, the health department hopes to open an on-campus HIV testing clinic by the end of the week, and plans to offer free tests to each of the school’s 1,300 students.

The investigation stemmed from a single HIV diagnosis, which the health department traced to students at the school. Officials will not disclose whether the person who tested positive is a student at Normandy.