A serious two-vehicle crash has shut State Highway 1 at Piarere in South Waikato and left five people injured

Emergency services were alerted to the crash, about 5.30am.

A witness on the scene moments after the crash, who would not be named, said both vehicles looked badly damaged.

“They were both pretty banged up, I could see the crash was still really fresh when we arrived, it had only just happened.”

The woman said she saw emergency services moving back and forth working to extract people from the vehicles.

“I saw the two cars facing towards each other and people still in them,” she said.

Hato Hone St John said five people have been taken to Waikato hospital with serious injuries.

They responded with five ambulances and two rapid response vehicles.

SH1 is blocked between Horahora Rd and Paparamu Rd.

The New Zealand Transport Agency advised motorists in a post online to consider delaying their journey or allow extra time for a detour using SH27 and SH29, via Hinuera.

Traffic management is being arranged, and motorists are advised to expect delays.

A Fire and Emergency New Zealand spokesperson told the Herald three people were trapped in one of the vehicles.

“We have been working to extricate them,” they said.

They have four crews on the scene from Putāruru and Tirau.

"State Highway 1 is blocked between Horahora Road and Paparamu Road and traffic management is being arranged.

"Motorists are advised to expect delays."