CONTENT WARNING: This article mentions sexual assault and criminal drug use.

Police in Queensland have named 35-year-old Matthew James Markcrow and 23-year-old Crystal Marie Sawyer as the couple accused of drugging several women and keeping them as sex slaves in suburban Brisbane.

Per ABC News reports, it is alleged that Markcrow recruited the “vulnerable” young women on social media, provided them with stupefying drugs, tattooed his name on them to mark them as property and forced them into illegal prostitution.

Four women, aged between 17 and 24, were found this week after a search of a property at Mount Gravatt East in Brisbane, but police said there may be more alleged victims. Officers say the women are now safe, and have encouraged any other victims to come forward.

The pair, who were arrested on Thursday, appeared in Brisbane Magistrates Court yesterday, after a four month investigation into the alleged sex slave ring. Markcrow remains behind bars, while his co-accused, Sawyer, has been released on bail.

He faces a variety of charges, related to unlawful prostitution, drugs, breaching privacy and conducting a business involving servitude. Inspector Juliet Hancock of the Prostitution Enforcement Taskforce said:

“We’ve been shocked by this, we didn’t think this was happening in Australia, let alone Brisbane. It’s something that you see that’s happening overseas… it’s quite hard to shock police. This is quite horrendous offending.”

The two are due to appear in court again later this month.