Police now suspect theatre director Veijo Baltzar of aggravated rape and aggravated child sexual abuse after new victims came forward.
Baltzar was already suspected of aggravated human trafficking related to his time running the Drom theatre company after a career spanning decades in Finnish cultural circles.
The new suspicions mean police have until June to charge Baltzar, after the deadline for completing the preliminary investigation was extended from February.
"Investigating this exceptionally broad case will take several months," said Saara Asmundela of Helsinki police. "As a result of the new suspected crimes there is now a lot of work to do, including interviewing dozens of witnesses."
"At this stage it is still possible that new victims will come forward," said Asmundela, who added that it was still unclear how many of the people to be interviewed are new victims and how many are witnesses.
Helsinki District Court remanded Baltzar into custody in November on suspicion of aggravated human trafficking.
In addition to Baltzar two other people are also suspected of aggravated human trafficking.