Detectives investigating the disappearance of a young mother more than 40 years ago are extending their search to a residential area in West Dunbartonshire.<br /><br />Mary Duncan was 17 years old when she disappeared from her home in Alexandria in 1976.<br /><br />The teenager, who had a 13-month-old daughter, vanished after telling her family she was going to meet a friend.<br /><br />Her daughter later died of natural causes.<br /><br />No trace of Mary has ever been found despite extensive inquiries.<br /><br />On August 17, police announced they were searching a number of sites at the Vale of Leven Hospital in Alexandria.<br /><br />Detectives have extended the search to include a residential site in Helensburgh, which will commence on Monday.<br /><br />Detective Superintendent Calum Young, from West Dunbartonshire CID, said: "This latest development is due to extensive enquiries carried out in an attempt to find any indication of where Mary could be.
