A woman has been arrested on suspicion of murdering a teenage girl who disappeared in July.
Cambridgeshire Constabulary said a woman in her 30s from Peterborough was detained on Saturday evening.
Bernadette Walker, 17, was reported missing from Peterborough on July 21 by her parents after she had not been seen for three days.
A man in his 50s from Peterborough, who was arrested on suspicion of Bernadette’s murder, remains in custody.
Police have been carrying out enquiries and searches in an attempt to locate Bernadette but a murder inquiry has now been launched.
Detectives from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit declared the case a “no body” murder investigation on Friday
Detective Superintendent Jon Hutchinson said: “Due to the length of time Bernadette has been missing and concerns she may have come to some harm, we made the decision to declare this a murder investigation.
“Whilst we hope we do find Bernadette alive and well, there is every possibility this may not be the case therefore my team and I will do everything possible to find out what has happened to her and bring any offenders to justice.”
Anyone with information on Bernadette’s whereabouts or what has happened to her is urged to contact police.