A prison van transporting nine inmates has overturned on a dual carriageway, leaving three prisoners needing hospital treatment, police said.
North Yorkshire Police said they were called to the incident on the westbound carriageway of the A64 near Tadcaster at about 5pm on Wednesday.
A spokesman said the van, operated by the G4 security company, was taking nine prisoners from Hull Prison when it was involved in a collision with two other vehicles and overturned.
He said six of the prisoners were unhurt and returned to the jail.
Three prisoners suffered "non-life threatening injuries" and were taken to York District Hospital for treatment.
He said the occupants of the other vehicles involved were unhurt.
The road was closed for a number of hours while investigations were carried out.