Serious crash blocks State Highway 1 near Sanson

Caroline Williams/Stuff

Emergency services are at the scene of a serious crash near Sanson. (File photo)

State Highway 1 has been blocked by a serious crash in Rongotea.

Emergency services were called to the scene of the two-vehicle crash near Sanson on the highway between Rowe and Rongotea roads at about 4.40pm on Friday.

A Hato Hone St John spokesperson said three ambulances, two rapid response vehicles and two operations managers were at the scene.

No one had been transported to hospital as of 5.20pm, however, at least one person had received serious injuries, he said.

Murray Dunbar, the central shift manager for Fire and Emergency New Zealand, said firefighters were assisting with traffic management and would help to clear the road once the patients had been assisted.

"There is a bit of a traffic backlog.

One car is on its side."

Diversions were in place at the scene, a police spokesperson said.

The NZ Transport Agency Waka Kotahi urged motorists to follow the directions of emergency services on site.