Doctors today confirmed five new cases of a virulent strain of tuberculosis - two students and three staff at the Crown Hills Community College in Leicester - bringing the total to 29.
British public health officials said they were searching for the source of the largest outbreak of TB in the country for 20 years.
They have extended a screening programme around the school to try and discover how far the disease has spread.
"This is a major outbreak. We are dealing with a particularly virulent strain . . . which needs minimal exposure to infect," said Mr Philip Monk, consultant in communicable diseases at Leicestershire Health Authority.
More than 700 students and teachers at Crown Hills Community College in Leicester have been screened for the disease.
Leicestershire Health Authority said another 60 students were found to have possibly been infected.
A Department of Health spokesman said health officials were now testing friends and family of those diagnosed with the disease, along with the rest of the children at the school.
Tuberculosis affects the lungs and is spread by coughing, sneezing or spitting. The disease can be fatal in small children but is usually treatable with antibiotics in adults.