A liquid waste tanker has overturned in an accident on a roundabout on the A39 between Truro and Falmouth.
Devon and Cornwall Police said three vehicles had been involved in the collision in Devoran at about 09:45 BST on Tuesday.
They said one driver had been released from their vehicle and, although injuries were not currently known, they were not believed to be life-threatening.
The road was closed at the top of Carnon Downs carriageway and police asked drivers to avoid the area while emergency services worked at the scene, although at 12:20 traffic monitoring service Inrix reported traffic was coping well.