Police are investigating whether murder victim Joanna Yeates could have been strangled with her own ski sock - which her killer might then have kept as a trophy.
The landscape architect's snow-covered body was found on Christmas morning missing one of her grey, knee-length socks, and detectives believe the garment may hold the key to solving her murder.
The 25-year-old - last seen alive nearly three weeks ago - was not wearing her coat or boots either but those items were recovered from her flat in Canynge Road, Clifton, Bristol.
On Thursday morning uniformed police officers searched drains in the streets surrounding Joanna Yeates's flat. An industrial drain cleaner was used to dredge up debris before police used sticks to work through the leaves and mud.
Police were also seen checking an old rifle range in the grounds of Clifton College, which is next door to Miss Yeates' home.
Det Chief Inspector Phil Jones, who is leading the murder hunt, held up a similar size-five sock on Wednesday to the one Miss Yeates was wearing.
He said: "The jacket and the boots have been found at her home address. That would indicate that Jo had returned home. However, at this present time the sock has not been found. It hasn't been found (where her body was) and it hasn't been found at her home address."
The detective said he was "keeping an open mind" about whether the killer or killers could be keeping the sock as some sort of trophy or whether Miss Yeates was strangled with it.
Following the appeal for the missing garment - the type bought in an outdoor shop - a man approached police outside Miss Yeates's flat and handed over a grey sock. The sock was put into an evidence bag but later police said at this stage it was not the sock they were looking for.
Mr Jones also confirmed that the killer or killers may have tried to put Miss Yeates's body over a wall into the quarry on Longwood Lane, Failand, North Somerset, but instead left her on the grass verge. "There are a number of theories about how Jo came to be in Longwood Lane and this is a possibility, yes," he said.