The three women - a 30-year-old Briton, a 57-year-old Irishwoman and a 69-year-old Malaysian - are believed to have suffered years of physical and mental abuse at the hands of a couple.
Police carried out house-to-house enquiries over the weekend in and around Peckford Place in Brixton, where the three women were found.
It has emerged that the couple - a man aged 73 and a 67-year-old woman - were previously arrested in the 1970s, although police have not said why.
They are of Indian and Tanzanian origin.
Officers have recovered a birth certificate for the 30-year-old woman, who is believed to have lived her entire life in servitude, but no other official documents for her have been found.
The case came to light after the Irish woman rang the Freedom Charity last month after seeing its founder Aneeta Prem in a Sky News report about forced marriages.
The Metropolitan Police said part of the agreement on October 25 when the women were removed from the address was that police would not take any action at that stage.
None of the women was reported missing after being rescued, police said. All three are now in the care of a specialist non-governmental organisation.
Some 37 officers from the Met's human-trafficking unit are working on the case.
On Sunday, Home Secretary Theresa May said tackling modern slavery in Britain was a "personal priority", saying many other victims were "hidden in plain sight" across the country.
"It is walking our streets, supplying shops and supermarkets, working in fields, factories or nail bars, trapped in brothels or cowering behind the curtains in an ordinary street: slavery," she wrote in The Sunday Telegraph.
"Something most of us thought consigned to history books, belonging to a different century, is a shameful and shocking presence in modern Britain."