Two people have been arrested in connection with the disappearance of 16-year-old Rebecca Watts from Bristol.
It comes after about 150 people joined a search for the teenager, during which a laptop computer was recovered.
Rebecca, known as Becky, was reported missing after failing to return home to Crown Hill, St George, on 19 February.
Avon and Somerset Police said the search for her continues while two people were being held in custody for questioning.
Darren and Angie-Mae Galsworthy, her father and stepmother, said: “We continue to hope that she will be found safe and unharmed, but we will prepare ourselves for the worst.
“We would like to take this opportunity to thank everyone who has assisted in the search for Becky and for the messages of support.
“We continue to work with the police to bring their investigation to a successful conclusion and we would like to ask members of the public to continue to report anything, however small, if they think it may help to find Becky.”
A laptop computer was found by members of the public searching for Rebecca Watts
Friends, family and local residents gathered at Oldbury Court estate to join the search
The recovered laptop was given to police who are yet to comment on whether it is significant, but the force said that when Rebecca went missing she had her own computer with her.
As well as her laptop, Rebecca had her mobile phone with her but no clothing when she went missing, the force said.
John Galsworthy, her grandfather, said the family were trying to remain strong as the search intensified.
Addressing those who had gathered, he said: “We are broadening the search.
“There are groups separate to ours who are going out using their own initiative, going wherever necessary to try and find her.
“We are continuing in the hope there may be something discovered today. We want everyone to keep their eyes and ears open.”
Detectives have previously searched Troopers Hill nature reserve as well as Rebecca’s family home, which is close to St George Park.
On Friday Det Supt Liz Tunks, head of Avon and Somerset Police’s major crime investigation unit, took over the case.
As part of the search, Mr Galsworthy said more than 6,000 leaflets had been printed, with around 1,500 more expected to be delivered next week.
At the scene: Maddy Ware, BBC Points West
Becky’s family was joined by friends and also members of the public who have never met Becky but have been moved by the story.
The family asked those joining the search to look for a laptop, a black iPhone and a dark-coloured puffa-style jacket.
Becky’s grandfather also said it was important for the family to keep busy as they try to stay positive and maintain their hope she’ll be found safe and well.