Emergency services were called to the scene of an accident near Ohau Pt, north of Kaikoura, at 3.45am today after a truck and trailer unit rolled on to its side and hit a bank.
The south-bound truck was carrying hazardous substances including sulphuric acid and paint, said Kaikoura Volunteer Fire chief Ian Walker.
The contaminants were contained before they drained into the water table or nearby waterways.
The driver of the truck escaped unharmed.
The scene is still being cleared and the highway will be down to one lane for the rest of the day, Mr Walker said.
The accident is the second in six days involving a truck roll near Kaikoura. The first was on Friday afternoon and was south of Kaikoura.
- The Marlborough Express