Traffic backed up after four-car crash on Harbour Bridge

Traffic is backed up on Auckland's Harbour Bridge following a four-car crash this morning.

Police received a call about 10.30am that four cars had been involved in an accident in the bridge's southbound lanes, police northern communications spokesman Richard Johnston said.

Lane 4 heading south is completely blocked off and motorists are being advised to avoid the area if possible.

It was not yet known what caused the crash and police did not know of any injuries, he said.

Police are still clearing the scene.

Meanwhile, police are also at the scene of a crash north of Johnsonville on State Highway One near Wellington.

There were no injuries but police warned commuters to expect delays.