A Department of Labour report into a rock fall that injured three people and closed closed State Highway 36 in the Bay of Plenty last year, has found all practical safety steps were taken.
The rock fall in the Mangorewa Gorge, between Tauranga and Rotorua in August, crushed a car, causing minor injuries to the occupants.
The road remained closed for many months.
The fall happened near a construction work site, where the road was being widened.
The department says no single cause for the rock fall could be found and contractors followed all expert advice to protect workers and the public.
No further action will be taken.