Police in Germany have arrested two brothers for locking up and raping a woman for days in a plush building with a sauna where they found three more potential victims.

The men – aged 37 and 23 – face kidnapping and GBH charges for sexually abusing the 26-year-old between the 15th and the 19th October at a three-story apartment building which features a basement sauna in Wallduern, a town with around 12,000 inhabitants in the southwestern state of Baden-Wuerttemberg.

The victim – whose name and age were withheld by investigators – eventually managed to contact a friend who subsequently called the police.

State prosecutors in Mosbach have refused to give any detailed information to ensure the success of the investigations into the case.

However, a spokesman for the authority confirmed that the 37-year-old main suspect was considered a “serial offender.”

His 23-year-old brother – who remains in custody – is regarded as his accomplice.

Police officers discovered three more women as they raided the apartment building, according to the local Rhein-Neckar-Zeitung newspaper. The nature of their connection with the case is being investigated.

The 37-year-old main suspect has been put into a closed psychiatric institution.

It has not been disclosed whether this was a preliminary measure and if a medical expert has already carried out a comprehensive evaluation of his mental state.