A man found unconscious, with head injuries, in a Masterton street remains in a serious condition in hospital.
Aged 40, the man was found about 6am on Saturday on a footpath on Essex Street.
Police say they don't know whether he was the victim of a crime.
He was initially taken to Masterton Hospital but has since been airlifted to the intensive care unit at Wellington Hospital.
A forensic examination of the scene has been conducted by the police and residents have been questioned.
The police are appealing for anyone who may have seen the man, described as European with brown hair, between 1am and 6am.
Five detectives are working on the case.