Married men using the services of prostitutes can expect a visit from police officers searching for clues to the disappearance of a teenage vice girl.

Missing Rachel Wilson kept in daily touch with her mother and her grandparents but vanished four weeks ago tomorrow.

Cleveland Police who are becoming increasingly concerned about 19-year-old Rachel reveal that customers of hers who fail to come forward to help, can expect a knock on the door.

Detective Sergeant Andy Greenwood disclosed: "We are in the possession of information which would lead us to people who used Rachel as a prostitute.

"Other prostitutes have given us information in relation to those people who regularly use prostitutes. We have details of people who regularly use prostitutes.''

Some 450 posters have gone up around Middlesbrough with a concentration in shops, cafes and pubs in the Woodlands and Southfield Road areas of the town where Rachel plied her trade. The 19-year-old drug addict is the third prostitute to disappear from the streets of Middlesbrough.

The remains of vice girl Vicky Glass, 21, were found on the North York Moors two years ago - her killer has not been caught - while there is still no trace of teenager Donna Keogh, who disappeared from the town in 1998.

Detective Superintendent Tony Hutchinson, the Force's most senior investigating officer, said he is keeping an open mind as to a link between Rachel's disappearance, Vicky and Donna.

He said yesterday: "We are still following a number of lines of inquiry but the more time that passes our levels of concern increase. It is almost four weeks since she had any contact with her family and that is completely out of character.

"We still need information and I would ask people, be they prostitutes or their clients, to come forward and help us. There have been a number of reported sightings of Rachel, but when checked they have turned out to be mistaken.''

Anyone who can help has the choice of ringing a specially set up incident room on (01642) 303187 or speaking direct to Mr Hutchinson on a dedicated mobile phone, 07740 070 624.