Quarantined British students and their teacher outside the Yanxiang Hotel
Four more UK school pupils have been confirmed as having swine flu after being taken to hospital in Beijing.
Four other British and four US pupils from the same trip have been diagnosed, and more than 100 of their classmates and teachers quarantined in a hotel.
China has this year quarantined hundreds of foreign visitors who have shown symptoms of the H1N1 virus.
The affected children are on a two-week cultural exchange trip, and come from several different schools.
Seven of the teenagers being treated are from London and one is from Somerset.
Four are from Parliament Hill School, Camden, three from the Central Foundation Boys School, Clerkenwell, and one is from Clevedon School, Somerset.
The British embassy in Beijing said about 50 British school children and teachers were currently being held in quarantine.
Among those with confirmed swine flu is Matthew Barnett, who told the BBC from his hospital room that he was feeling "OK".
Some of the British teenagers holed up in a hotel room in Beijing
While the other three were found to have high temperatures when they arrived at Beijing airport earlier in the week, Matthew fell ill later.
"I was at the hotel because they have routine temperature tests and my temperature was higher than usual so I had to be brought here.
"They put me in this separate room and said 'you have to stay in here and not make contact with anyone else'. I've been treated fine, they've been very nice and the food's very good."
His mother Jackie, in London, said she was relieved that Matthew was on the road to recovery.
"We were obviously quite worried when we first heard, and it was about 24 hours before we could speak to Matthew. But once I spoke to him it put my mind at rest that he was being treated well."
Matthew had been in good health before he left for China, she said. "He's always been very healthy."
More than 600 Britons are on the trip, organised by the SSAT, the Department for Children, Schools and Families, the British Council and Chinese organisation Hanban.
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A SSAT spokesman said: "We are following the Chinese health regulations.
"We don't know at the moment if the students will be able to continue with their trip or come home."
Among those in quarantine was Sandra Marsh's 15-year-old daughter Katharine, from Cranbrook in Kent.
Mrs Marsh told BBC News that those held back at Beijing's Yanxiang Hotel had been sitting in the same section of the plane as the boys who took ill.
"What was quite worrying was how the Chinese team collected the children. They turned up armed in contamination suits, put them on an ambulance and took them away.
"The children were very frightened at the beginning. Now they're fine and they're being well looked after in the hotel, although they're having swabs taken every day.
Chinese health officials monitor passengers arriving in the country
"This holiday of a lifetime has just been destroyed."
The American children had been in contact with the UK group and four were also diagnosed as having the virus.
Simon Calder, travel editor for the UK's Independent newspaper, said many countries were using "thermal imaging" at airports to test travellers, and the UK was viewed as a high-risk area.
China's Health Ministry said on Friday that 1,537 cases of swine flu had been reported in the country of 1.34 billion. None have been fatal.
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