Police investigating the disappearance of Christchurch woman Emma Campbell warn she may never be found.

A $10,000 reward for information about missing Nelson man Leo Lipp-Neighbours has been extended for another three months.

Stefan Jensen, who suffers from mild dementia, disappeared on June 4 from his son's rural property in Pukekawa, 24km southeast of Pukekohe.

Police investigating the apparent killing of Raymond Piper say people have reported sightings of two cars linked to the case.

Police say they have evidence missing Kapiti man Raymond Piper has died a violent death.

Raymond 'Son' Piper has not been seen since May 15 when he disappeared from Paraparaumu.

Police are still working through possible sightings of a vehicle that might have been involved in the disappearance of missing Kapiti Coast man Raymond 'Son' Piper.