Traffic is crawling on Auckland's Southern Motorway after two crashes in nearly the same spot just 15 minutes apart during morning rush hour.

Vehicles are banked up for more than 10km after two smashes in the southbound right lane just before the Southeastern Highway offramp.

The NZ Transport Agency warned rush hour traffic was heavy from the CBD and to expect delays.

The first crash blocked the right lane about 8am.

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Just as it was clearing a secondary crash blocked the same lane, adding to morning traffic woes.

A police spokeswoman said the first smash involved three cars.

No one was injured but two of the three vehicles were so badly damaged they needed to be towed away.

The second crash in virtually the identical placed happened at 8.15am when a car clipped the motorway's concrete median barrier.