A second pre-school in Singapore has had a teacher diagnosed with active tuberculosis this month - and at least one of its pupils has been diagnosed with a latent form of the disease.

Bridges Montessori in Punggol, said to have about 50 pupils aged 18 months to seven years old, discovered on Aug 12 that a foreign trainee teacher had been diagnosed with the disease.

Its director, Ms Irene Toh, told The Straits Times that 29 children and seven staff were screened for TB eight days ago, although results were confidential. However, a mother of a pupil told The Straits Times anonymously that her daughter was diagnosed with latent TB.

She took her for a follow-up screening at Tan Tock Seng Hospital yesterday on the advice of doctors, and said that while there, she met two other mothers of children from the pre-school who had similar appointments.

For the next nine months, they will have to go for monthly appointments to ensure the latent disease does not turn active.

Ms Toh said the trainee teacher had spent three weeks at the school as an observer.

The woman, who has not been identified, is recovering and on medical leave.

Parents were informed of the case and the pre-school was fumigated and sanitised.

The teacher was deemed to be medically fit by her own country before being diagnosed with TB here.

Ms Toh said the teacher received a work permit as she did not have active TB when she applied.

"We did our due diligence before taking her in," she added. "Now, she plans to return to her home country to be with her family."

In a separate case, on Aug 17, a teacher from China at Little Greenhouse pre-school in Bukit Batok also contracted active TB. She is on medical leave and undergoing treatment.

The pre-school told ST yesterday that contact screening tests were completed on children over the past week. Results will be released to parents over the next few weeks.

As an additional precautionary measure, staff members as well as children under the age of five from Little Greenhouse will undergo further chest X-ray screenings.

Correction note: In an earlier version of this article, it was stated that TB is a virus. This is incorrect. We are sorry for the error.