VANCOUVER - There's no telling how many high-rise brothels may be in Vancouver, according to one expert.

UBC Faculty of Law assistant professor Benjamin Perrin, an expert on human trafficking, says condos - such as the one in Yaletown where 29-year-old Jeffrey Bian was stabbed to death June 11 - make for great illegal brothels.

"They blend into the community, which makes it difficult for police to identify, and offers johns a higher level of discretion," he said.

Perrin wasn't fazed to learn the suspects in Bian's murder may have been robbing a number of brothels across the city.

"There's a great deal of money being made," he said.

"It's not surprising they would become the target of armed robberies, just like grow-ops are."

Vancouver police told media Monday that the nature of the businesses means robbery victims are unlikely to come forward.

Perrin says Crime Stoppers operators were recently trained in human trafficking and the sex trade, and offered the anonymous tip line as an alternative - especially for women forced into the trade and looking for protection.

Matt Kieltyka reports for Vancouver 24 hours.