The two-vehicle crash on Parnassus Rd (SH1), near McPhersons Stream Bridge in Hurunui, was reported to emergency services at 8.33am on Monday.
A police spokesperson said initial indications on Monday morning showed there were serious injuries and "motorists should avoid the area".
In a statement on Monday evening, police said one person has died following the crash in Spotswood.
"Sadly, despite best efforts, one person died in hospital.
"The Serious Crash Unit and Commercial Vehicle Safety Team have attended and conducted scene examinations."
Fire and Emergency NZ said two trucks were involved in the crash. One of the trucks then caught fire.
"One person was trapped in the burning truck, but has since been removed," a Fenz spokesperson said.
Fire crews from the Cheviot, Scargill, Culverden and Hurunui stations were working to put out the fire.
Hato Hone St John was also called to the crash. Two helicopters and two ambulances responded.
NZ Transport Agency Waka Kotahi said SH1 was closed between Cheviot and Spotswood. Diversions were in place.
Southbound traffic should take the detour from SH1 via Waiau West Rd Rd at Spotswood, then turn left onto Leamington Rd, left onto Munro Rd, and right onto Ward Rd through to Cheviot. The reverse applies for northbound traffic.
"The detour route is not suitable for heavy vehicles. Heavy vehicles should use Leader Road East, Rotherham Rd and State Highway 7," NZTA said in a statement.
