The Fairfax County Health Department has expanded its investigation of tuberculosis cases that originated at Lee High School, asking that an additional 60 people be tested for the disease.

The department announced last week that three people at the Springfield school had tested positive for the bacterial infection, which generally attacks the lungs. The disease, which can be spread through coughing, sneezing and laughter, is potentially deadly if not treated quickly.

The Health Department initially identified about 400 students and 30 staff members at Lee High who medical experts said had a high risk of exposure to the original three cases. All were offered free testing to determine whether they were infected. About 292 people have been tested so far, school officials said.

School Board member Tammy Derenak Kaufax (Lee) said 60 more people were contacted June 25 about getting tested. They may have come into contact with the three people confirmed to have the disease through extracurricular activities.

Students and staff at other Fairfax County schools are among those 60 people.

Health Department spokesman Glen Barbour said that, because of the large number of possible exposures, additional positive tests are expected — although he said the new cases would not necessarily be connected to the original three at Lee.

“They are pieces of a puzzle, and we have to put them all together,” Barbour said. “It’s not ‘CSI’ like you see on TV, where the investigation is over in 60 minutes. It’s important in public health cases to ensure all the steps are taken and that we go through the process methodically.”

One of the Lee High TB cases was diagnosed in December, and the other two were confirmed in June. One of the two June cases was only coincidentally connected to the school, Barbour said; the Health Department concluded that the person did not contract the disease at Lee.

Last year, the Health Department investigated about 90 cases of tuberculosis. To date, the county has looked into about 30 cases in 2013.

According to the Virginia Health Department, about 235 TB infections were reported statewide last year. Of those, fewer than 30 cases involved people 24 or younger.

In Fairfax County, known for its multicultural population, most TB cases originate overseas, Barbour said.