Herbicide leaked from spilled containers after a heavy truck carrying freight crashed on State Highway 8 near Tarras early yesterday.
The south-bound freight truck, owned by Transworld Roxburgh Ltd, rolled on to its side on a 45kmh corner near Camp Creek, south of the Lindis Pass, about 20km from Tarras about 2.15am yesterday.
Police said the 52-year-old driver was freed from the cab by firefighters and flown to Dunstan Hospital with minor injuries.
The crash reduced traffic to one lane, and a small amount of herbicide leaked from containers on board.
Transworld director Geoff Smith, of Roxburgh, said the driver had 12 months' experience of the Christchurch to Alexandra route.
Sergeant Simon Paget, of Cromwell, said the police commercial vehicle investigation unit was looking into the crash.
