Traffic on the N2 just outside of Grahamstown has come to a standstill following a fatal accident on Saturday morning.
Police Spokesperson Captain Mali Govender says the driver of a water tanker lost control and overturned.
His passenger is in a critical condition.
She says he was on his way to deliver water to farms in the area.
The road is still closed in both directions and will re-open as soon as the scene is cleared up.