A teenage girl has died at a campsite and three other people have been taken to hospital with suspected carbon monoxide poisoning.
West Mercia Police said officers were called to the site in Bucknell, South Shropshire, by the ambulance service at around 10am today.
Detective Inspector Gavin Kinrade said: "I can confirm that we are working with the Shropshire Fire and Rescue Service to investigate this incident.
"We are treating the girl's death as unexplained, but at this stage there do not appear to be any suspicious circumstances."
West Midlands Ambulance Service said a man and woman and a young boy, believed to be 11 years old, were taken from the scene to the Royal Shrewsbury Hospital.
A spokeswoman said: "Crews arrived at the campsite to find CPR being carried out on a girl who was in cardiac arrest.
"Ambulance crews continued resuscitation efforts in an attempt to restart the girl's heart. Sadly, despite their best efforts nothing could be done to save the girl and she was confirmed dead on scene.
"A boy, believed to be 11 years old, was suffering from suspected carbon monoxide poisoning.
"Crews and the doctor began oxygen therapy and, due to his serious condition, the boy was airlifted to Royal Shrewsbury Hospital for emergency treatment. Paramedics continued to monitor the boy's condition on route to hospital.
"A woman and man were also given oxygen therapy by ambulance crews before being taken by land ambulance on blue lights to the same hospital for further treatment."