No new clinical tuberculosis cases have been found at Butler High School beyond the three people diagnosed with the disease last year, according to the most recent test results released Monday by the Richmond County Health De­partment.

The department returned to the school in January and Feb­ruary to retest 242 students and staffers who had negative skin tests from the first round of testing at the end of 2012, according to a news release.

The retests were seen as a safeguard because it can take up to three months for people with the disease to react to a skin test, according to the department.

Testing began in October after a Butler student was diagnosed with tuberculosis by a doctor.

The health department performed skin tests on those who were in close contact with the girl, then expanded the testing to include the entire school and staff.

In October and November, 578 people were tested and 136 were positive for tuberculosis bacteria.

Three of those were confirmed to have the disease.

According to the Centers for Di­sease Control and Pre­vention, a person who has been exposed to tuberculosis bacteria and shows a positive skin test still might not have contracted the disease.

Those found with clinical tuberculosis from Butler were not allowed to return to work or school or go to public places until they were considered non-infectious, according to the news release.