Two crashes, including a six-car smash, are creating mayhem on Auckland's motorways.

Six cars collided on the Mangere Bridge at about 6am. Fire and Emergency said nobody was trapped and there were no reports of injuries.

The NZ Transport Agency said the crash had blocked two of the four lanes southbound on the Mangere Bridge.

Traffic has backed up to Waterview Tunnel as tow trucks begin to clear the wreckage.

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NZTA advises motorists to expect delays and those travelling to the airport to consider using the southern motorway (State Highway 1) through Manukau.

Meanwhile northbound on the Southern Motorway a 6.25am crash briefly blocked the right lane north of Reagan Rd overbridge.

The lane has been cleared but NZTA also advises motorists there to take care and expect delays.