Traffic in Auckland is starting to flow normally now following an earlier breakdown that caused a huge backlog towards the North Shore.

A NZ Transport Agency spokeswoman for the Auckland region said just before 9.30am that congestion had now reduced and traffic was returning to normal.

It comes after a truck broke down on a south-bound lane, on the Southern Motorway, just after the Fanshawe Rd offramp shortly after 6am.

The breakdown blocked that lane for sometime and led to about a 20km backlog of traffic congestion on the Northern Motorway over the Harbour Bridge and towards Greville Rd, in Albany.