A nine-year-old boy in critical condition in hospital after falling from a moving coach in Norfolk may have been injured after a door opened suddenly, police have said.
The boy, who was returning to his home in Lincolnshire after playing in a tournament in Norfolk for Stamford Rugby Club, was hurt after the incident on the A47 near King's Lynn.
Norfolk Police confirmed the boy's father was travelling on board the 71-seater double-decker coach while his mother travelled in a car as part of the convoy.
The coach is being held in a secure compound where it is being examined by police and officials from the Vehicle and Operator Services Agency.
Inspector Chris Brooks said: "This is a very difficult time for the boy's family and we have specially trained officers supporting them.
"As a result of initial inquiries we know just prior to the incident that people were queuing for the toilet.
"Somehow, the door has opened and the boy has fallen from the moving coach.
"We will also be speaking to other people who were on board at the time of the incident and it would be inappropriate to speculate on possible causes at this stage."
The boy has been transferred from the Queen Elizabeth Hospital in King's Lynn to Addenbrooke's Hospital in Cambridge.
Anyone who witnessed the incident should contact the serious collision investigation team at Norfolk Police on 101.