A person has been seriously injured in a two-vehicle crash that blocked Auckland’s Northwestern Motorway.

The accident on State Highway 16 blocked two of the three citybound lanes after the Lincoln Rd on-ramp.

Police earlier advised motorists to avoid the motorway or delay travel.

The lanes were expected to stay closed for some time as the Serious Crash Unit investigated.

Traffic on the Northwestern Motorway. Photo / Google Maps

Google Maps earlier showed gridlocked traffic on the motorway for 4km from the Lincoln Rd on-ramp back to the Hobsonville Rd on-ramp.

All lanes have since been cleared.