One of the women who died in a copycat double suicide pact contacted police to complain she was being harassed, it has emerged.
The woman, who has not been named, fled to a flat in Putney, south-west London, owned by a not-for-profit trust that helps vulnerable women.
Neighbours said she appeared scared and was reluctant to speak to people as she kept her curtains drawn night and day.
One said she moved to the affordable bedsit about five months ago from Roehampton to "escape someone" and because of people taking drugs near her home.
Officials at the Independent Police Complaints Commission launched an investigation into the reaction of police to her complaints. They received a referral from Metropolitan Police detectives after they found records of her contacting the force on a database, it is understood.
The bodies of two women, both believed to be in their 20s, were found at the second-storey flat in Norman Court, Lower Richmond Road, on Thursday morning.
Investigators believe they gassed themselves using a toxic combination of chemicals after sealing doors and windows.