Fred West cops may quiz wife Rose in jail as they search Gloucester cafe for vanished teen Mary Bastholm, 15

The work is expected to take about two weeks, with Detective Chief Inspector John Turner saying it is expected to reveal "once and for all" if Mary was buried at the site.

The major breakthrough comes days after a 39-strong police team led by three archaeologists began analysing the basement of a café in Gloucester, half a mile from West’s home at 25 Cromwell Street.

They are working in an area to the side of the basement which builder West converted into toilets. The material and "suspected bones" are under a partition.

A source said: “Camera images clearly show material which matches the navy blue coat Mary was wearing when abducted.

“In addition, there are images of what look very much like human bones.

"Great care is being taken to sift through the surface.”

Gloucestershire Police had received possible evidence from a TV production company to suggest the body of the missing teenager could be buried at the location.

And cops said excavation work will take place after “anomalies” were found during the search which started on May 7.

Officers are in touch with West's son Stephen after it is said that he admitted killing the teenager - but refused to confirm this to police.

Detective Chief Inspector John Turner said: "The analysis from our experts and the material provided by the production company means there is enough evidence to justify excavation work beginning.

"I've spoken to the family and was so impressed by their quiet dignity and gratitude for all the work we've done and will be doing.

"They understand it is possible we won't find human remains but they also know that we will do everything we can to establish if Mary is buried at this location.

"This will be slow and painstaking work but we have the best people on it and I can reassure our communities that all involved, from my team of investigators, our scenes of crime officers, search officers and family liaison officers to the forensic archaeologists who will continue their work are absolutely committed to the job ahead.

"In the meantime, I continue to ask for patience and understanding from all those affected by our ongoing presence at the cafe and thank everyone who has helped us in the last 10 days."

West was a regular at the café, where Mary worked as a waitress before she went missing in January 1968.

He killed himself aged 53 in 1995 while awaiting trial for 12 murders — but admitted he did 20 more.

Mary’s family said in a statement released by police: "Senior investigating officer John Turner has sat with us and explained the ongoing investigation as well as his intentions to excavate the cafe to try and find Mary.

“We are extremely happy Gloucestershire police is continuing to try and search for Mary and this gives us a chance to potentially put her at rest after all these years.

“We want to thank everyone who has wished us support through this distressing time, and we are continuing to be in close touch with the investigation team, and are being kept up to date with any new developments.

“We hope this is a chance to finally get closure for Mary and would like to continue to ask for privacy whilst the excavation is ongoing.”

West's wife Rose, 67, is serving a whole life tariff for ten murders and could be quizzed over any remains that are found.