The HSE has confirmed a teacher at a south Dublin school has contracted TB but is refusing to reveal how many pupils have been infected.

One parent told the Sunday Tribune the number of pupils at St Pius boys national school in Terenure who have been infected could be as high as 20, but the school and HSE have refused to comment.

The school found out the female teacher had contracted TB when contacted by the HSE. She is thought to have contracted TB during the summer holidays, while the children were diagnosed last week. The pupils were in an infant block of three classes with about 25 pupils in each. Initially only pupils from the teacher's class were tested, but the HSE then extended the tests to adjoining classes.

"A small number of pupils reacted positively for latent or dormant TB which can't be transmitted. It's not contagious," said school principal Dermot Lynch.

One parent whose child tested positive said: "If it's not transferable, how come my son has it?"

The HSE said: "The HSE can confirm that an adult associated with St Pius Boys' National School was diagnosed with tuberculosis and is receiving the appropriate treatment.

"The Department of Public Health is working in close consultation with the school to ensure appropriate procedures are followed."