A nine-year-old boy has suffered "life-threatening injuries" after falling from a coach, police have said.
Officers in Norfolk said nobody else was injured in the incident, on the A47 trunk road near King's Lynn.
The incident happened at around 3.45pm today.
A police spokesman said: " The boy has been taken to the Queen Elizabeth Hospital in King's Lynn with life-threatening injuries.
"A number of other people were on board the coach at the time and no other passengers were injured."
The road is expected to remain closed for some time and local diversions have been put in place.
Anyone with information is asked to contact police.
A total of 20 children and 10 adults were on board the 71-seater coach at the time of the incident.
The youngsters are from Stamford Rugby Club in Lincolnshire and were travelling home after playing in a tournament at Holt in north Norfolk when the incident happened.
Superintendent Dave Marshall said: "This is a serious incident which has left a nine-year-old boy fighting for his life.
"The circumstances of how the boy came to fall from the coach will form part of our investigation and it would be inappropriate to speculate further at this stage.
"The boy's parents, who were travelling with the teams, are being supported by specially trained officers."