BERLIN (AP) — A swimming instructor in southwestern Germany is suspected of sexually abusing 40 young girls, and using an underwater camera to film some of the abuse.

Baden-Baden prosecutor’s office spokesman Michael Klose told the dpa news agency Wednesday that the 33-year-old man, whose name wasn’t released, was first arrested in September in connection with six cases following an investigation of parents’ complaints.

Klose says after further investigation, the man’s now suspected of 136 counts of sexual abuse of girls ranging in age from 4 to 8 in the Baden-Baden area from October 2015 until his arrest. Klose says he also intimidated at least two victims, with the “threat that he would kill them.”

The man denies the charges and has refused to cooperate with police. An indictment is expected in April.