Two people have been arrested in connection with the disappearance of 16-year-old Rebecca Watts from Bristol.
Avon and Somerset Police said that two people from the St George area of Bristol were being questioned, with the girl missing for more than a week.
More than 1,500 people have joined in the search for Rebecca, and a laptop has been found by searchers.
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."
Police said the recovered laptop was handed in to them, and have yet to reveal whether it was significant for the investigation.
They said that Rebecca had her computer and mobile telephone with her when she went missing after leaving home at 11am on 19 February, said police.
There have been no reported sightings of her since.
Officers have searched St George park, near her family home, and are planning to trawl nearby lakes and rivers, the force announced.
Thousands of leaflets have been distributed and a social media campaign launched in the search for Rebecca.
Becky is described as 5ft 4in and slim, with long, bright red hair and was wearing a dark navy blue Puffa jacket with fabric sleeves.
Anyone with information is asked to contact Avon and Somerset Police on 101, or Crimestoppers on 0800 555 111.