All lanes are open on Auckland's Southern Motorway after a large truck jack-knifed.

The stricken truck was left straddling three lanes of the motorway, leaving the key route south impassable for around 15 minutes.

The NZ Transport Agency warned motorists the jack-knifed truck was creating long delays.

Queues had banked up for nine kilometres to Manukau.

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Police diverted motorists off at Hill Rd.

Drivers heading out of the city were told to avoid the motorway until the crash was cleared.

Police said the truck was shifted off the motorway about 15 minutes after it lost control and traffic was flowing again.

NZTA said even though the truck was cleared traffic was now heavy between Takanini and Manukau heading south.

It warned motorists to expect delays.