The 21-year-old University of Otago student was home alone, studying for exams, when the attack took place inside the Scobie Rd home between 1.45pm and 2.15pm, Detective Senior Sergeant Steve McGregor, of Dunedin, said.
The woman had phoned her mother, who worked nearby, after becoming alarmed at noises coming from elsewhere in the house, he said.
The mother arrived home a short time later to find her daughter unconscious in her bedroom, with a head injury and what was believed to be the weapon used in the attack lying nearby, Det Snr Sgt McGregor said.
He declined to say what sort of weapon had been used and it was not known how the intruder had entered the house.
Some personal property had been disturbed, but it was not known whether anything had been stolen.
A scene guard was posted outside the house yesterday and the property was later taped off.
Det Snr Sgt McGregor said police were treating the investigation "quite seriously".
"We are keeping an open mind as to the motive. It could have been a burglary gone wrong. Obviously, the more sinister side is they [the offender] have gone there for a more sinister motive," he said.
The woman was treated at the scene by St John ambulance staff before being taken to Dunedin Hospital.
She remained in hospital in a stable condition last night, having regained consciousness.
Her injuries were not believed to be life threatening, Det Snr Sgt McGregor said.
• Anyone who may have seen a person or vehicle entering or leaving the vicinity of 54 Scobie Rd between 1.45pm and 2.15pm yesterday is urged to contact Detective Sergeant Chris Henderson on (03) 471-4800.
