A double-decker bus was “teetering” on a roadside bank after leaving the road between Falmouth and Truro.
The Roselyn bus was travelling towards Truro and left the road near Playing Place.
West Briton photographer Jonathan Jacobs was on the scene. He said: “It’s teetering on the edge. It’s come off the road and it’s causing chaos here.”
Police said the bus collided with a hedge after trying to avoid a fallen tree.
The road remains open and police are in the area directing traffic but there are major delays in both directions.
Nobody is understood to have been injured in the incident.