A woman has told police she was raped at a house where serial killers Fred and Rosemary West lived.
The alleged victim is understood to have been illegally brought to the UK as part of a sex trafficking ring.
The woman said she was attacked at 25 Midland Road in Gloucester where the Wests' daughter Charmaine was murdered in 1971.
Three people have been charged with trafficking women into the UK for sexual exploitation.
Iveta Viragova and Votjech Virag, both from Tooting south-west London, and Ludmila Nistorova, of Raglan Court, Gloucester, face five charges each, including conspiracy to traffic for sexual exploitation and immigration offences.
Three men arrested in the Czech Republic are currently subject to extradition proceedings.
It is understood the investigation started after one victim escaped from the gang and reported them to police.
The Wests tortured, raped and murdered an unknown number of women over a 20-year period.
Fred West was charged with 12 murders, but committed suicide in a Birmingham prison before his trial.
Rosemary West was convicted of 10 murders in November 1995 and is serving a life sentence.