A smoking truck blocking part of the left lane of State Highway One, northbound, just after the Harbour Bridge tonight.
A Fire Service spokesman said the truck had a problem with its brakes, which was causing it to smoke, and crews had left the scene as they were unable to help.
Initial reports suggested the truck was on fire.
The New Zealand Transport Agency advises motorists to pass with care.
All lanes are now clear, but congestion remains heavy past the scene.
