Detectives hunting the killer of Joanna Yeates are taking DNA samples from her Facebook friends.
They are swabbing dozens of people across Britain as calls for mass screening in her home city grow.
Those targeted include men who live more than 100 miles from the murder scene.
Officers are convinced that Miss Yeates, who was missing for eight days before her body was found a short drive from her home on Christmas Day, was killed by someone she knew.
The landscape architect had up to 200 friends on the website. Police are also asking for background information about her life and her relationship with her boyfriend Greg Reardon.
Police are also studying phone records after it emerged from one of Jo's friends that she sent her last text at 8.20pm.
Jo invited Matthew Wood out for a drink in the message but because he was at a Christmas party he didn't reply until 9.20pm. He told The Sun of his subsequent anguish at the fact that Jo didn't reply, but police hope the new information will help them determine what time she was strangled.
Police forces in other parts of the country are assisting with taking the DNA samples and conducting interviews.
One of Miss Yeates’s friends, who lives more than 100 miles from Bristol and had not seen the 25-year-old for several weeks, had a swab taken from the inside of his cheek last week.
As for her relationship with Greg, it was solid, they were happy and a great couple.
It is now 24 days since Miss Yeates was last seen alive.
Avon and Somerset Police insist they are ‘happy’ with the progress of the investigation.
But a source said: ‘A meeting has been called at the highest level to address major concerns.
‘There is a growing feeling that the inquiry team has too many young detectives on it. The longer the investigation goes on, the bigger the need for some old hands and detectives with 25 or so years of experience.’
Miss Yeates was last seen alive on December 17, when she was out for a drink with friends.
Her landlord Christopher Jefferies, 65, was arrested on suspicion of her murder and released on police bail. He denies any involvement.