A seven-year-old boy has died at an open air museum after suffering head injuries in an accident involving a steam-powered traction engine.
Durham Constabulary said the youngster was pronounced dead at the scene of the tragedy at the Beamish Museum, which has since been evacuated.
A police spokeswoman said the driver of the engine and its trailer had been taken to hospital suffering from shock after the incident, which happened shortly before 3pm on Sunday.
In a statement issued by Durham Constabulary, Inspector Steve Dowdle confirmed that officers were alerted by the ambulance service and were now conducting a joint inquiry with the Health and Safety Executive.
Insp Dowdle said: "The engine driver will be spoken to by police at an appropriate time and is being treated as a witness.
"The identities of those involved are not being released, but it is understood that neither of them were visitors to the museum. Detectives and roads policing officers are at the scene to establish exactly what took place and the Health and Safety Executive is also at the scene."
The museum's director Richard Evans also issued a statement through police.
Mr Evans said: "We are naturally shocked and our thoughts are with the boy's family at this time. We took an immediate decision to close the museum for the rest of the day as we support the joint investigation."
The Beamish Museum preserves life as it was in 1913, complete with trams, a working farm and a school. Among its attractions is a mid-19th century drift mine, which was reopened as a tourist attraction in 1970.
Witnesses to the accident are urged to contact Durham Police by dialling 101.