Homicide detectives have been left baffled by the discovery of two decomposed bodies in an apartment in Sydney's south west.
The sisters — aged 23 and 24 — are believed to be foreign nationals and were found dead in separate bedrooms in their Canterbury home.
Their landlord had not received rent for "several weeks", prompting a visit from authorities, which sparked an investigation with few leads.
With no visible signs of a break-in at the property nor injuries to the bodies, mystery surrounds the circumstances leading up to the deaths.
Forensic police have dusted the apartment for fingerprints, while detectives seized bags of potential evidence and cameras from the front of the building.
Investigators have been door-knocking residents as well as speaking to the building's postman after reports of a build up of parcels and letters outside the mail boxes.
Neighbour Kim Bui said she was shocked and saddened by the tragedy.
"I'm scared, I'm worried, I'm just trying to protect my children so I don't know what happened," she said.
"Yesterday I saw police cars outside. I asked the gentleman and he said there were two girls in level one and they died, and what happened I really don't know, but it's pretty scary."
Detective Inspector Claudia Allcroft said officers would be relying on the results of a post-mortem to determine the next course of action.
"A post-mortem examination will be conducted tomorrow and we hope to have further information once that has been completed," she said.
"There are no obvious signs of injury at this stage — we're still in the early stages of the investigation."
Detective Inspector Allcroft said the deaths were being treated as suspicious.
"It's a very very tragic scene — very sad circumstances," she said.
"We're looking into all lines of inquiry — if anyone has information about these sisters or anything suspicious in the area — we would urge you to contact police or crime stoppers."
