Mass searches for missing teenager Gaia Pope are taking place in Dorset.
Volunteers have formed human chains to scour three locations around Swanage, where the 19-year-old went missing on 7 November.
It follows the release of a third murder suspect on Friday, as police inquiries continue.
Her sister, Clara Pope-Sutherland said: “We are choosing to believe that the murder investigation is just a formality and that she is alive.”
Hundreds of volunteers have joined searches, which set off from three car parks in Swanage at about midday to comb rural areas for possible clues.
Miss Pope-Sutherland said the response from people in the town had been amazing and she was “beyond grateful”.
On Thursday, police discovered clothing belonging to Miss Pope on open land outside Swanage.
The case is being treated as a murder inquiry, but her sister said the missing person investigation had not been dropped either.
Miss Pope-Sutherland said the discovery of the clothes was “positive” as police now had “some kind of lead”.
So far three people have been arrested on suspicion of murder, including Paul Elsey, 49, who was released under investigation on Friday afternoon.
He lives with his mother Rosemary Dinch, 71, who, along with her 19-year-old grandson, Nathan Elsey, was arrested on suspicion of murder on Monday.
They have also been released under investigation by Dorset Police.
Murder detectives have been focusing their forensic investigations on homes, cars and an area near the coast path where clothing belonging to Miss Pope was found.
BBC reporter Laurence Herdman said the search teams had been out overnight again, and the case had left the town “subdued”.
“Everywhere you look you see posters of Gaia”, he said.
Miss Pope-Sutherland said community searches had visited “pretty much every house” in Swanage to hand out posters and ask people to search their properties.
Earlier this week, her mother urged people to look in vans, garages and houses in case she was being kept against her will.
The search for Gaia
7 November: Miss Pope is driven by a family member from Langton Matravers to Swanage. At 14:55, she is seen on CCTV inside St Michael’s Garage buying ice cream and at 16:00 her last confirmed sighting is at an address in Manor Gardens on Morrison Road
8 November: Her family make a personal plea through the police for her to get in contact. Ch Insp Steve White, of Dorset Police, says the force is “becoming increasingly concerned”
9 November: Dorset Police renews its appeal to find the 19-year-old. Searches have been carried out in the Swanage area, with support from the coastguard and police helicopter. Miss Pope’s family release a statement saying they are “frantic with worry”
10 November: CCTV footage is released of Gaia on Morrison Road, Manor Gardens, at 15:39 on 7 November.
13 November: Search warrants issued at two addresses in Swanage. Rosemary Dinch and Nathan Elsey are arrested on suspicion of murder and later released under investigation
14 November: Searches continue with the coastguard and volunteers from Dorset Search and Rescue and Wessex 4×4
15 November: CCTV images of Miss Pope at St Michael’s Garage are released. Searches continue to concentrate inland, supported by neighbouring police forces
16 November: Paul Elsey is arrested on suspicion of murder. Women’s clothing is discovered in a field near Swanage and a police cordon is set up
17 November: Paul Elsey is released while police inquiries continue.