Police hunting for missing 12-year-old Tia Sharp have sealed off an area around her grandmother's home, where she was last seen a week ago.

More than 20 officers arrived at The Lindens on the New Addington estate, near Croydon, south London, and placed a cordon around the property where Christine Sharp, 46, lives.

Detectives at the scene declined to explain what the cordon was about.

But Scotland Yard said the area was sealed off as part of pre-planned search and that a media briefing that had been arranged with Area Commander Neil Basu had been postponed.

Media and the public had previously been able to walk past the terraced house, from which Tia vanished last Friday. But the police cordon prevented anyone from getting within about 100 yards.

Earlier in the day, Mrs Sharp broke down as she spoke about Tia's disappearance. She said: "My only message to Tia is that I love her. She is my life. I don't know where she has gone. I don't know how she's gone. She's not staying away by choice, I know this. I just don't know what else to say."

Mrs Sharp's partner, Stuart Hazell, 37, is believed to have been the last person to see Tia. He told police she was heading to the Whitgift Centre in Croydon to buy flip-flops and agreed to be back at her grandmother's terraced property by 6pm.

Mr Hazell, who was interviewed as a witness, has said another witness saw her leaving the house shortly after midday and therefore he was not the last person to see her after having spent Thursday night alone with Tia.

Police began the new search after a flurry of activity at the house. A search dog was in the property for 30 minutes, Mrs Sharp was driven away by officers and bags of evidence were also removed.

Speaking at the scene, Detective Chief Inspector Nick Scola, who is leading the investigation, said officers were carrying out a "pre-arranged search" which was likely to "take one or two days". White-suited forensics officers arrived this afternoon and began a search of the house.