The unexplained death of a five-year-old girl from Buckinghamshire is being investigated by Thames Valley Police.
Police were called by medical staff at Wycombe Park Hospital, High Wycombe, on Monday where the child had been taken by ambulance.
The death is not being treated as suspicious at this time, police said.
A post-mortem examination on the girl, who lived in High Wycombe, is due to take place. Police are liaising with medical staff, a spokesman said.