Emergency services were called to the A19 between Riccall and Barlby at around 2pm this afternoon.
The force's Forensic Collision Investigation Unit tweeted: "We are attending a serious RTC on the A19 at Riccall. Road will be closed as we investigate the scene."
It has been reported that a lorry and mobility scooter were involved in the crash.
A North Yorkshire Police spokesman said earlier that he could not give any further details, but said the road would remained closed for several hours.
Arriva Yorkshire said the closure meant that all its 415 services were severely delayed.
It said buses are following a diversion through Skipwith and there was only a limited service to and from Riccall at this time.
In an update issued at around 7pm, police said the road had now been reopened to traffic.
No further information has been issued about the circumstances of the crash or any injuries sustained.