Two people had been badly injured, one critically, in a two-car crash on State Highway 57 near Shannon.
Emergency services were called to the crash at 11.25am.
One person has critical injuries and another is in a serious condition, police said in a statement.
A Fire and Emergency NZ spokesman told 1 NEWS people were trapped. He did not know how many people.
Crew from Levin, Foxton and Shannon were in attendance, the spokesman said.
The road is blocked and diversions are in place at the intersections of SH 57/Tavistock Road and SH 57/Shannon-Foxton Road.