Crash blocks State Highway One southbound lane near Tawa

A serious crash between a car and a truck has blocked the southbound lane of State Highway One near Tawa, north of Wellington.

Emergency services were called to the crash - on the stretch between Transmission Gully and the Tawa-Grenada North off-ramp - about 8.10pm on Wednesday.

Police said one person is in a critical condition.

They advised southbound motorists to avoid the area or expect delays, as the Serious Crash Unit would be examining the scene.