The A57 in Worksop has been shut after a serious crash involving a number of vehicles.
Six people are believed to have been injured in the collision at 12.55pm.
Police said the extent of their injuries is not yet known.
An air ambulance has attended the scene.
The closure, between the junctions with the A60 and Claylands Avenue, is expected to remain in place for some time so drivers are advised to seek alternative routes.
Anyone who saw the crash or has dash-cam footage should call police on 101 or Crimestoppers on 0800 555 111, quoting incident number 408 of May 28.