Inquiry head Detective Inspector Greg Williams told media last night: "There are elements at the scene that indicate at least one of the deaths was possibly a homicide - so it certainly is a homicide inquiry."
Asked if police were looking for any other people in connection with the deaths, he said it was "early days" in the investigation.
"I've got two people up there ... and we are open-minded on what has taken place."
The two bodies had not been formally identified yesterday, but were believed to be a Waimate man and woman, with police appealing for information about a Waimate man reported missing by family on Sunday.
He is Jason Frandi (43), who has lived in Waimate for some time.
Det Insp Williams would "not rule out" the male body was that of Mr Frandi, but emphasised no formal identification had been made.
He said good progress had been made identifying the woman, but her name would not be released until next of kin had been notified.
Formal identification will be one focus of police today.
They are continuing to search for a vehicle that the man and woman used, or was used to transport them, to the area where their bodies were found.
They were discovered about 11am on Saturday by riders on a Waimate Main School fundraising trail ride around a 40km loop in Waihaorunga, a remote area with access off Pentland Hills Rd.
Some of the riders who discovered the bodies said the man was aged in his late 30s or early 40s and was still warm when found. The woman's body was found in a clearing away from the man.
Police were called and the event stopped.
Det Insp Williams said seven detectives had been brought from Christchurch, police from Timaru and Oamaru were assisting and Environmental Science and Research forensic staff arrived early yesterday to work at the scene.
He declined to reveal what injuries there were to the bodies, saying that was for the coroner.
The bodies were taken by helicopter late yesterday to Christchurch, where postmortems will be carried out today.
Police are also focusing on Mr Frandi. His car, a silver, 1997 BMW 328 saloon, registration ATT 530, was last seen parked at his Waimate address about 11am on Saturday.
He is a male caucasian, with a "No 1" haircut, solid build and extensive tattoos on his arms and backs of both hands.
Anyone who saw or had contact with Mr Frandi or saw his vehicle after 11am on Saturday is asked to phone Waimate police on (03) 689-7272.
