Toronto police have laid additional charges against a 23-year-old man in a human trafficking investigation that began in January.

Police say the suspect, Simon Ho-On, was arrested on Wednesday and charged with 17 new counts, including assault, sexual assault and forcible confinement.

He was initially charged in February with human trafficking-related offences, after he and another man allegedly forced a 22-year-old woman to work in the sex trade.

Investigators alleged in the earlier case that Ho-On used a noxious substance to render the woman unconscious, and that he tattooed her body with his nickname, "Sosa."

Police say additional witnesses and alleged victims have come forward since they announced those initial charges.

They say they're concerned there may be more alleged victims, and they're asking anyone with information to contact police.