On Wednesday, things that belonged to 26-year-old Jesse Baird (ex-Network 10 host) and 29-year-old Luke Davies were found in a bin in a suburb of the city.
Local media have named a guy as a police officer who used to date Mr. Baird as someone who can help with their investigations.
But the police told the BBC they couldn't be sure who the person was.
The New South Wales Police Force said in a statement that detectives would "continue to look at all past relationships and associations."
At Mr. Baird's home in the Paddington area, police found blood and moved furniture. This is about 28 km (17 miles) from Cronulla, the neighborhood where the couple's things were found in a bin by a worker.
Some of the things that were found were clothes covered with blood, a phone, and credit cards.
What the police think is that the couple was in Paddington on Monday. 7NewsAustralia got a hold of CCTV video that seems to show the couple going into Mr. Baird's flatshare.
The news source said that cops were also looking at CCTV footage that showed a white van in the area.
Police say that flight attendant Mr. Davies hasn't talked to his family or been to work since Monday.
According to Det Supt Jodi Radmore, all possible lines of inquiry are being looked into. She told reporters, "We do believe that there has been some kind of incident based on the crime scene at Paddington and the property located at Cronulla."
She also said that made the police "very worried about one or both of their safety."
"Witnesses described a verbal argument," she said, "but it wasn't reported to police at the time ... it was only reported to police yesterday [Monday morning] during canvassing."
The police in New South Wales are asking for help.