They believe the witness, who was parked a mile from the scene of the murder in Aston, may have seen the suspects shortly afterwards.

Detectives say it is a significant lead into the investigation of the murders of Charlene Ellis, 18, and Latisha Shakespeare, 17, on 2 January.

The girls were killed outside a New Year's party at a hairdressing salon in Birchfield Road.

The timing and location of this incident leads me to believe that these may well have been the cars and people involved in the shootings Detective Superintendent Dave Mirfield

The witness reported seeing three men pulling up in a Vauxhall Vectra car and being acknowledged by a man in a red car which pulled up alongside it, blocking the road.

The location, at the junction of Victoria Road and Upper Sutton Street in Aston, was on the shortest route from the scene of the killings to the Aston expressway.

Detective Superintendent Dave Mirfield said: "The timing and location of this incident leads me to believe that these may well have been the cars and people involved in the shootings."

Police are appealing for anyone driving along the road between 0410 GMT and 0430 GMT who saw the cars to contact them.

Charlene's twin sister Sophie and 17-year-old Cheryl Shaw were also injured in the incident - all four girls were cousins.