reports.
A source claims Stephen passed the information on to Chief Superintendent John Bennett, who led the West murder case, but was dismissed.
Stephen said previously: "My dad told me that he'd been working on the cafe at the time she went missing and that one day the police would find her there.
"I said to him, 'Did you do it? You've always denied it'. He said 'yeah, I did do it. I did take her'."
Detective Chief Inspector John Turner confirmed his team have now visited Stephen to explore what his dad told him regarding Mary's disappearance.
DCI Turner also said cops could quiz Rose West , who is serving a whole-life term at HMP New Hall, if anything "significant" is found.
Rose was an accomplice in most of Fred's murders and is serving life in prison Credit: PA:Press Association Police at the cafe today as they prepare to continue their search Credit: Alamy A worker with a power drill at The Clean Plate cafe in Gloucester Credit: The Sun The work could take around two weeks Credit: Alamy Speaking about Stephen's help in the case, he said: "The trouble with that is, Fred often lied to the investigating officers throughout the investigation.
"So just because Fred said it, it doesn't mean to say it's true."
It comes after six "anomalies" were found at the cafe where missing Mary is feared to be buried.
Specialist technology discovered holes in the concrete floor of toilet cubicles at the Clean Plate cafe in Gloucester where the serial killer carried out renovations.
Mary , 15, was working at the establishment before she disappeared in 1968.
The team used a ground penetrating radar and found a void in the basement of the cafe within two toilet cubicles.
They drilled the area, allowing holes for ventilation so that police dogs could get an indication of human remains.
The insertion of an endoscope in one of the holes also identified a grainy image of a 'blue looking material within the gap.'
Six 'anomalies' were found in the basement of the cafe Credit: PA Police are concentrating on an area West converted into toilets Credit: PA Mary was last seen wearing a blue coat and blue and white dress when she vanished from a bus stop.
Cops are now 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.
DCI Turner said the work is expected to take around two weeks and could reveal "once and for all" if Mary was buried at the site.
He added: "There is a possibility that we will be speaking to Rose West.
"But what’s important now is that we review and excavate what is in the basement.
"What I’m saying is, there is something that looks like blue material within the void. What I’m not saying is: ‘That’s Mary Bastholm’ before we find any human remains."
Detectives searching for Mary Bastholm have found possible evidence linking her to the scene Six anomalies have been found while police search the cafe Police and archaeologists are specifically analysing an area to the side of the basement which builder West converted into toilets Detectives began to search the site in Gloucester after a TV documentary into West was aired 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.
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.
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.”
Police have continued digging up the Clean Plate Cafe as they search for Mary Monster West was working as a builder at the time Officers confirmed it is being searched in relation to Mary's disappearance