He said police were following up a number of leads from the victim's interview, and were waiting on medical results for more information.
"There's been a medical examination and there might be some forensics that come out of that.''
Police had also carried out a leaflet drop in the area, but no information had led to the offender's whereabouts.
He said police still wanted to speak to the owners of a grey Honda Odyssey sporting a Tongan flag, as the victim had walked out in front of the car.
"We are chasing this Honda Odyssey to rule them out of the enquiry.''
Police would also like to hear of any sightings of the woman.
The victim was now receiving counselling after the incident, he said.
Hospital spokeswoman Lauren Young said hospital staff were taking extra care since the attack last week.
"Police are patrolling the area more frequently and we're offering staff security guards to escort them to the carpark.
"Everyone is obviously more vigilant. Staff have been advised not to travel alone, not to walk alone to the carpark, and not to wear iPods so they can't hear their surroundings.''
She said there had been no more reports of suspicious behaviour.
The attacker was described as a young Polynesian wearing a grey Adidas hoodie and a black beanie with a red eagle on it. He may have sustained facial injuries during the attack.
Anyone with information about the hospital attack should contact Detective Sergeant Andy Townsend on 09 353 0023 or call Crimestoppers anonymously on 0800 555 111.