In the case of an alleged serial offender who is said to have held and raped a woman for days, the investigators assume at least two other alleged victims.
A spokeswoman for the Heilbronn police headquarters said on Friday.
The victims are also women.
The spokeswoman did not say what he should have done to them.
Investigators are currently checking to see if there are other victims.
A 37-year-old is said to have held a 26-year-old against her will in Walldürn in northern Baden-Württemberg from October 15 until the night of October 19 and violated her.
The victim finally managed to use a phone from the property to call an acquaintance who alerted the police via the emergency call, the spokesman said.
The young woman is said to have told her acquaintance that she was being held against her will and feared for her life.
Investigators did not provide any information about the woman's injuries or condition.
Some of the suspects are said to have commented on the matter
According to the public prosecutor, the suspicion of other alleged victims arose, among other things, when the crime scene was searched.
At least one of the two suspects is said to have lived in the property in Walldürn (Neckar-Odenwald district).
The suspects had partially commented on the matter, said the spokesman.
The 37-year-old man is accused of taking hostages in combination with particularly serious rape and dangerous bodily harm.
He was taken to a psychiatric hospital with a placement arrest warrant.
This indicates that the man may be mentally ill or had reduced criminal responsibility at the time of the crime.
The investigators initially did not provide any further information on request.
The man's 23-year-old brother is said to have helped with the alleged crimes.
He was arrested on suspicion of being an accessory and taken to a correctional facility.
swe/dpa