The man was in or near the apartment when police arrived at the scene, after neighbours reported that the woman had fallen to the ground from the second floor.
"He is familiar with the woman. We are investigating what kind of relationship it is," says Ola Österling, press spokesperson for the police.
The woman was taken to hospital by ambulance, where police were later able to briefly interview her. The extent of her injuries is otherwise unclear. Both people are between 20 and 25 years old, according to Österling.
The incident occurred during the night of Saturday.
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