Police are searching a Gloucester cafe in connection with the disappearance of a teenage girl suspected to have been murdered by serial killer Fred West.
Mary Bastholm vanished in 1968 aged just 15 and her body has never been found.
West, who died in prison in 1995 aged 53, was previously suspected over her disappearance.
Officers from Gloucestershire Police were called to the Clean Plate cafe in Southgate Street by a production company filming a documentary there.
The company had reported it had found possible evidence to suggest a body could be buried within the property.
Officers are expected to be there for several weeks, the force said.
West, one of Britain’s most prolific serial killers, committed at least 12 murders between 1967 and 1987 in Gloucestershire, the majority with his second wife, Rosemary.
All the victims were young women. Their dismembered bodies were typically buried in the cellar or garden of the couple’s Cromwell Street home in Gloucester, which became known as the “House of Horrors”.
Fred is known to have committed at least two murders on his own.
In 1994 he admitted murdering his daughter Heather, while Rose is known to have murdered Fred’s stepdaughter, Charmaine. The couple were apprehended and charged in 1994.
But Fred took his own life while awaiting the murder trial the following year.
Gloucestershire Police said its major crime investigation team has deemed further assessments are required at the cafe in order to determine whether an excavation is necessary.
A white tent was erected outside, with police officers stationed at the front of the building and a police van parked nearby.
Other officers were seen carrying evidence bags out.
Family liaison officers have now been put in place to provide support and updates to Mary’s family.
A statement from them said: “We are aware of the ongoing developments around Mary’s disappearance and are being kept up-to-date.
“At this time, please may we ask for privacy so we can grieve for Mary.”
Assistant Chief Constable Craig Holden said: “This could be a significant development on a case which has gained a lot of public interest over the years.
“On the basis of the information provided to us, we consider this to be new and potentially important evidence in the case of Mary Bastholm, however further detailed assessments will take place over the following few days to determine the extent of excavation needed.
“First and foremost our thoughts are with Mary’s family and we would ask that their privacy is respected at this difficult time.
“This news may understandably alarm those who work near to the premises, as well as those in the wider Gloucester community and beyond.
“The Constabulary has always said any fresh evidence would be reviewed.
“This has happened and a focussed and proportionate investigation will now take place.”