Police are still trying to piece together the final movements of killer Jason Frandi and his victim, Czech tourist Dagmar "Dasha" Pytlickova.
Police today released new photos of Frandi's silver BMW with the hope new witnesses would come forward.
Detective Senior Sergeant Marion Neill, who heads the investigation, said officers were focusing on the movements of Ms Pytlickova and Frandi on the afternoon of Saturday, May 26.
Their bodies were found in a remote forestry block in the Waitaki Valley the next day.
Frandi is believed to have assaulted and murdered Ms Pytlickova before taking his own life.
"The last confirmed sighting we have of Frandi was in Waimate at 12.17pm and we are keen to piece together his movements up to that time that the bodies of Frandi and Dasha were discovered on Sunday," Ms Neill said.
"At this stage the last confirmed sighting of Dasha was in a gravel area on State Highway 8 near the Cromwell bridge between 3pm and 3.10pm. We believe she was attempting to hitchhike to South Canterbury.
"We are continuing to follow up possible sightings but we still have gaps in what we know of the movements of both people."
Frandi's vehicle was a 1997 two-door silver BMW with registration ATT530.
Ms Neill said between 15 and 20 detectives were working on the case.
Staff from Oamaru are investigating in the Waitaki Valley area while Central Otago detectives are interviewing people who knew Ms Pytlickova.
Detectives from Timaru are contacting more than 300 participants in the Waimate Main School charity trail bike ride, some of whom discovered the bodies.
"We are keen to speak to as many participants as possible so that we have a clear picture of exactly what was seen by the riders that afternoon," Ms Neill said.