Eleven members of a children's choir were taken to hospital suffering from diarrhoea and vomiting after arriving back in the UK from South Africa.
Medical staff checked 60 members of the Only Kids Aloud choir from Wales after they arrived at Heathrow Airport from Cape Town via Dubai . Eleven were taken to Hillingdon Hospital in west London but were later discharged.
The children's choir, with members aged between nine and 13-years old from across Wales had performed at sell out concerts in Cape Town.
They sang with Welsh opera star Bryn Terfel on Friday and Saturday night.
Bet Davies, of the Wales Millennium Centre in Cardiff, which formed the choir, said the group was now on its way back to Wales.
She said: "Some were sick on take off, some on landing and some during the turbulence, so because of the rules in the airline industry - we were travelling with Emirates - they say if more than three children are sick on the same flight you need to have paramedics in to check on the children.
"We were also anxious that they were checked out before travelling back to Wales as we have a duty of care towards them."
She added: "The medics say it could have been somebody with a bit of a bug before they travelled or it could be a combination of what I describe as nausea , tiredness and not drinking enough."
"We have been in Cape Town, we flew out on Tuesday, we have been on a very intense programme - they performed Friday night to Saturday night to sell-out audiences in Cape Town Opera.
"There were an audience of 1700 people on the gala night on Saturday and they had a standing ovation. They went to Robben Island on Saturday where they were shown around by a former political prisoner. They have had a life-changing experience. They were on a high.
"They have been rehearsing intensely over the past few days and they have not had that much sleep."
A spokeswoman for London Ambulance Service said: "We were called at 0741 to reports of a number of children taken unwell on a flight to Heathrow. We sent a number of resources to the scene including four ambulance crews, our hazardous area response team and a paramedic on a bicycle.
"Our medics checked over 60 children aged between 10 and 14 years old and we took eleven to Hillingdon Hospital suffering from diarrhoea and vomiting."