The incoming German mayor found at home with stab wounds named her daughter as a suspect in the attack, police have said.
Officers said that Iris Stalzer - due to take office next month in Herdecke, in the Ruhr region, after being elected on 28 September - was found with multiple stab wounds on Tuesday.
German police said Ms Stalzer is now in a stable condition, and was found sitting in a chair with multiple stab wounds before being taken to hospital in a helicopter.
Emergency services were alerted shortly after midday by her 17-year-old daughter, who reported that Ms Stalzer had been seriously wounded outside her house in an attempted robbery.
Both the mayor-elect's daughter and 15-year-old son were taken into custody.
In an update on Wednesday, police investigator Jens Rautenberg said Ms Stalzer pointed to her daughter as the suspect during questioning.
Officers also determined that the attack appeared to have happened indoors, found two knives and clothing believed to have been used, and determined there was no sign of a political motive.
Prosecutor Bernd Haldorn said he considers it a case of bodily harm, and officials intend to release the children and put them in the hands of youth welfare.
That office could then decide on further measures while the investigation continues.
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Ms Stalzer - an employment lawyer - is part of the centre-left Social Democrats and beat a centre-right Christian Democrat candidate to secure her new job.
German Chancellor Friedrich Merz responded to the attack on social media and said: "It must be swiftly investigated. We fear for the life of the mayor-designate and hope for her full recovery."