Police are digging up a garden at the former home of a paedophile couple who were friends with Fred and Rose West.
David and Pauline Williams are believed to have met the Wests while they were running the Prince Albert pub in Gloucester, where they also began to abuse children in the 1980s.
The abuse continued after they moved to Exeter in the 1990s, where they ran the Victoria Inn.
Scaffolding has been erected in the garden at the bungalow where the couple last lived in Cullompton, Devon, before they were jailed.
Devon and Cornwall Police confirmed the enquiry related to the previous owners and that they were excavating the garden following a tip-off.
Fred and Rose West
Twelve officers have been working at the site.
A police spokesman said: "Following intelligence received, Devon and Cornwall Police are undertaking excavation work at a property in Cullompton, Devon.
"This relates to historic intelligence connected to the address and its former occupants."
Officers said the work was expected to last another two days.
A mother who gave her name as Suzanne described the Williams as "eerie".
The excavation in Cullompton
"It was very eerie the fact that they didn't speak to anyone and they just came across as strange," she said.
"They were very solemn, they didn't smile, they didn't make eye contact."
Police said after the Williams' trial in November 2015 that the couple had been found guilty of 48 individual and joint charges stretching over 15 years.
David Williams was jailed for life after being found guilty of a number of offences including 11 counts of indecent assault, 10 counts of rape, two counts of gross indecency with a child, three counts of indecency with a child, two of cruelty and two cases of aiding and abetting an indecent assault.
Pauline Williams has been sentenced to 12 years in prison plus four years extended license after she was found guilty on two counts of aiding and abetting rape, two counts of aiding and abetting an indecent assault, and three counts of indecent assault.
The Wests were charged with the murders of young women over a 20-year period.
Fred West hanged himself in 1995 while awaiting trial, while Rose was convicted of 10 murders and sentenced to life the same year.