A truck has run off the motorway at Papakura, north off the Karaka on-ramp.
NZTA Auckland and Northland tweeted there had been a crash on the Southern Motorway north-bound after the Papakura off-ramp.
The left lane was blocked and traffic was warned to expect delays.
A Fire Service spokesman said it was a "truck versus tree" situation.
A truck had crashed into the motorway barrier and into a tree.