An outbreak of tuberculosis has struck at a Belgravia nursery school, according to the Health Protection Agency.
Seven children at Knightsbridge Kindergarten in Eaton Square are receiving a six-month course of antibiotics, and another 26 have TB in their bodies but no active infection, the HPA said.
These children are receiving a three-month course of antibiotics.
Pupils and staff at the school were tested after an adult linked to the shool was diagnosed in July.
An HPA spokesman said: "Some further tests are still being examined and because TB can be difficult to diagnose in children, it's possible that some children may require further tests to ensure they're properly diagnosed and treated if necessary.
"It's too early to say why so many children and adults have been infected and we'll be looking into this over the coming week. A possible explanation for this may include that the initial case was particularly infectious and had been suffering from symptoms for eight months before doctors had diagnosed TB."
"We have also been working very closely with the local NHS who have worked tirelessly to arrange special clinics for all the children concerned at very short notice."