A Malaysian woman, 69, an Irish woman, 57, and a Briton, 30, were rescued on October 25 by Freedom Charity and Scotland Yard recently after they underwent what is thought to be the UK's worst case of modern-day slavery.
The women were found following phone conversations between the charity and the 57-year-old, who had secretly gained access to a phone, Aneeta Prem, founder of Freedom Charity said.
"Two people arrested on Thursday, 21 November, in connection with an investigation into slavery and domestic servitude have been bailed until a date in January pending further enquiries," a police statement said.
Police said the arrested couple were not British nationals and it was "very unlikely" that the alleged victims were related to them because of their nationalities.
Prem said her organisation was investigating how the women had remained hidden for so long.
"In a very busy capital city we often don't know our neighbours. We're looking at people who were kept against their will in an ordinary residential street in central London," she told the BBC.
"She was able to use a phone but that was done in a very secret way. The people in the house didn't know she had it.
"It was a process of just over a week where there was lots of phone calls and they gained the trust of the charity, and by doing that they felt confident to reveal enough information," Prem said.
"Obviously the police were involved, and they managed to walk out of the house when nobody was around. We were waiting for them with the police and we managed to get them to a place of safety.