17 people, including two ambulance crew, are being treated after a suspected carbon monoxide gas leak.
Four ambulances went to the scene in Connor Downs, near Hayle in Cornwall, according to Cornwall Fire and Rescue Service.
A spokesman for the West Country Ambulance Service said 17 people in total have so far been affected, including two of its paramedics, and that the number might rise further as more people were checked over by medical staff.
"Our ambulances were first on the scene," he said.
"None of the people involved is in a life-threatening condition."
He said the two ambulance personnel had been taken to the Royal Cornwall Hospital in Truro for treatment but was unable to confirm how many other victims had so far been taken to the hospital.