Police investigating the deaths of Czech tourist Dagmar Pytlickova and Jason Frandi near Waimate are appealing for sightings of Frandi's vehicle in the hours leading up to the deaths.

Detective Senior Sergeant Marion Neill said police were focused on establishing the movements of Pytlickova and Frandi on the afternoon of May 26.

"We are today releasing further photographs of Mr Frandi's car in the hope that it may prompt people to come forward with information or sightings of the vehicle," she said.

Neill said there were still gaps in the movements of Pytlickova and Frandi.

"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 the time that the bodies of Frandi and Dasha were discovered on Sunday,'' she 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 hitch-hike to South Canterbury."

Up to 20 detectives are working on the case.

Staff from Oamaru are conducting inquiries in the Waitaki Valley area  to gather information from the public, while Central Otago detectives are interviewing acquaintances of Pytlickova.

Detectives from Timaru are contacting more than 300 participants in the Waimate Main School charity trail bike ride, some of whom found the bodies in a remote forestry block in the Waitaki Valley.

"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," Neill said.

Frandi's vehicle is a 1997 two-door silver BMW, registration ATT530. Anyone with information is asked to call the Timaru police on 03 687 9808.

- © Fairfax NZ News