A nine-year-old girl sustained fatal injuries when she was kicked by another horse while riding her pony.
Paramedics were called to a farm in Miserden, near Stroud, Gloucestershire, at about 11.25am on Saturday.
The girl is believed to have been out riding with The Cotswold Hunt when the incident occurred.
She was airlifted to Gloucestershire Royal Hospital in Gloucester where she later died.
"My understanding is that she was riding slightly behind a bigger horse that kicked out at her pony," a source said.
"The kick caught her. It was a tragic accident."
Another source said: "She is believed to have been kicked off her horse by another horse. It is an extremely sad incident."
It is unclear whether the girl suffered chest or head injuries in the incident.
A spokesman for Gloucestershire Police confirmed that the incident was not being treated as suspicious.
"Officers were called to a farm at Miserden at around 1pm on Saturday April 2," the force spokesman said.
"A nine-year-old girl was taking part in an organised event when she was involved in an incident involving a horse.
"The girl suffered serious injuries and was taken to Gloucestershire Royal hospital by air ambulance where she sadly died.
"The coroner and the child's family have been informed. Police are not treating the death as suspicious."
South Western Ambulance Service NHS Foundation Trust attended the scene with Wiltshire Air Ambulance.
"At 11.25am on Saturday we received a report that a female child had been involved in an incident with a horse," a spokeswoman said.
"We attended with a rapid-response vehicle, an ambulance crew, a doctor and an officer, and the air ambulance.
"She was flown in a life-threatening condition to Gloucestershire Royal Hospital."