Ten new cases of swine flu in England have been confirmed by health officials.
Another seven adults and three children have contracted the disease, taking the total number of UK infections to 65, the Health Protection Agency said.
The news came as four schools reopened after being closed when pupils became infected with swine flu.
The freshly-confirmed infections are spread across the country, with two in London, four in the east of England, three in the north west and one in the south east.
Medical experts are continuing to investigate another 336 possible cases of the disease.
In London, an adult and a child who both had close contact with patients who had already been confirmed as infected with swine flu.
In the east of England, an adult who recently visited the US, a child who recently visited Mexico, an adult who had close contact with a previously confirmed case, and an adult whose source of infection remains under investigation.
In the north west, two adults who recently visited Mexico and an adult who had close contact with a previously confirmed case are being examined
In the south east, a child who recently visited the US is also under investigation.
The Health Protection Agency stressed that the time taken to diagnose swine flu meant that the patients confirmed as infected may already have recovered and be symptom-free.