Police have been given several different descriptions of the suspect and hope that video evidence collected from surveillance cameras will establish the man's identity.
"We have received descriptions indicating that it could be a person with dark skin, while another witness believes the perpetrator was light-skinned. Now we hope that the footage from a surveillance camera at the site can provide us with concrete information," said Per Einar Flatås at Trondheim police.
The woman, who is reported to be in her 20s was assaulted and raped in the early hours of Friday morning. Residents in the area around Fjordgata in Trondheim notified police of what they thought was an ongoing rape.
A witness furthermore chased the suspect but he managed to evade capture.
The victim was on Friday recovering from her ordeal at St.Olav 's hospital in the city.
The suspect has been described described by police as a young man in his early 20s. He is about 170 centimetres tall, thin and has short dark hair. He was wearing a white t-shirt and dark pants when he was last seen.
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A large number of police were engaged in the search for the suspect in Trondheim on Friday morning and the crime scene has been examined by police technicians. Preliminary interviews have been conducted with the victim and three witnesses.
"The woman will be called in for a formal interview when she is up to it," Flatås said.