The partner of the grandmother of 12-year-old Tia Sharp has been arrested on suspicion of murder.
A Scotland Yard spokesman said that Stuart Hazell, 37, was arrested in a public place at 8.25pm in the south London borough of Merton after he was identified by a member of the public.
"He is currently in custody at a South London police station," added the spokesman.
A manhunt was launched after police hunting for Tia found a body at the house where she was last seen alive in New Addington, near Croydon, south London. The body was found at the home Hazell shared with Tia's grandmother Christine Sharp. The body has not yet been identified, and officers did not reveal exactly where the body was discovered.
The announcement that a body had been found came just a few hours after police began a forensic search of the terraced house. Hazell was interviewed by police as a witness on Wednesday but then released.
Mrs Sharp, who left her home with police shortly before Friday's search began, told reporters on Friday morning that her boyfriend was out helping in the hunt for Tia. She said that Tia's mother Natalie was "in bits" and she did not know where she was as "she needed to get away".
After she left, a cordon was placed around the house on The Lindens and white-suited forensics officers were seen going inside. Until then, journalists had been able to approach the house, although at times reporters were met with hostility from family members.
Police defended their handling of the case, with commander Neil Basu, the area commander responsible for south east London, saying officers' priorities were to support Tia's family and identify the body which had been discovered, as quickly as possible.
He said: "Clearly there will be many questions about the investigation into Tia's disappearance and I want to take this opportunity to clarify some of the speculation. When police investigate cases as difficult and challenging as this, it is important that we do not just focus on one line of inquiry.
"For example we had over 60 reported sightings of Tia, 800 hours of CCTV footage to examine and 300 plus calls into the incident room. All of these lines of inquiry were in the process of being followed up."