Four Barrie residents have now been charged with several offences as part of an ongoing labour human trafficking investigation.
In February, police said 43 victims were freed after 12 search warrants were executed in Barrie and Wasaga Beach.
Most of the victims were men, aged between 20 and 46, and found to be living in squalid conditions.
Police said they had been brought to Canada under the pretense of being here for an education, the promise of work permits and eventual permanent residency status.
Once in the country, investigators said they were forced to work for a cleaning company at locations in Collingwood, Innisfil, Oro-Medonte and Cornwall.
After paying fees, police said the vicitms were left with as little as $50 a month.
The suspects are three women, aged 19, 24 and 54, and a 51 year old man.