Detectives have sealed off a section of river in the hunt for the murder weapon used to kill teenager Lucy McHugh.
The 13-year-old was found stabbed to death in woodland near a sports centre in Southampton on 26 July.
An area of Tanner's Brook, close to Bindon Road and Warren Crescent, is being searched for clues.
Police are also appealing for sightings of a man who was seen riding a dark mountain bike on 25 July, the day Lucy disappeared.
The man, described as wearing a dark jacket and blue jeans, is thought to have been riding from Southampton Sports Centre along Coxford Road or close to Tanner's Brook.
Det Supt Paul Barton, of Hampshire Constabulary, said: "We have reason to believe that the murder weapon - a knife, scissors or other sharp implement - was discarded in this area and we are focusing our searches there.
"As part of our investigation, we are also looking to identify a man we believe cycled from the sports centre to this location that morning."
The force has undertaken a massive operation since Lucy's body was discovered, with officers handing out leaflets in Southampton to "jog people's memory" about the hours leading up to her death.
On Monday, friends and family of the schoolgirl gathered in Southampton for her funeral.
A 24-year-old man arrested on suspicion of murder and sexual activity with a child has been bailed.
The same man appeared in court on 31 July charged with withholding information relating to the case by allegedly failing to disclose his Facebook password to police.