Three women whose sister disappeared more than 40 years ago say they still hope that she will be found so that their family can be "complete again".

Mary Duncan went missing as a 17-year-old in West Dunbartonshire in March 1976.

Despite a major police investigation, no trace of the Bonhill teenager was ever found.

Her sisters told BBC Scotland that police could excavate land in the area in the search for Mary who's 60th birthday will be marked by the family this Saturday.

Marion McFarlane told the broadcaster: "It would be wonderful for us to get her back, especially at this time.

Evening Times:

In July last year, Mary Duncan’s sisters Debbie Rennick, left, Mandy Duncan, centre, and Marion McFarlane made a public appeal for information to try and find out what happened to her (PA)

"We should be having a birthday party, buying balloons and celebrating Mary's 60th birthday with her and her children and maybe grandchildren.

Read More: Mary Duncan: Family’s appeal for sister missing for 42 years

"That's a whole generation that is missing from our family."

Mary, who had a 13-month-old daughter, vanished after telling her family she was going to meet a friend. Her baby later died of natural causes.

Sister Debbie Rennick told the BBC: "Over the years we've come to realise she is no longer alive. But this investigation gaining momentum has given us hope that we might get some kind of resolution."

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Mandy Duncan added: "We just want to finish it and bring her home so our family is complete again."

A Police Scotland spokeswoman said: "We are not in a position to confirm any details. This is still an ongoing inquiry."