One person has been seriously injured after a vehicle hit a pole in Unsworth Heights on Auckland's North Shore.

The crash caused power lines to be downed and forced the closure of a road.

The road was likely to be closed all night, Auckland Transport said.

Police attended the crash at 4.55pm at the intersection of Sunset Rd and Meadowood Drive.

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It is understood there was only one occupant, the driver, in the vehicle.

St John said they transported one person to the North Shore Hospital in a serious condition at 5.50pm

Sunset Rd between Meadowood Drive and Trias Rd is closed and several power lines are down.

Another crash caused traffic to become heavy on Auckland's Southern Motorway.

Traffic was heavy between Symonds St and the South Eastern Arterial route after a crash on Penrose Rd.