Police want to talk to a student in connection with the death of Martine Vik Magnussen, 23, whose body was found in a central London basement.
Ms Vik Magnussen moved to London last year to study business
The Norwegian was found under rubble in a Great Portland Street block of flats on Sunday. She had neck injuries.
Police want to interview fellow student Farouk Abdulhak, 23, who lived there.
Mr Abdulhak was with her last Thursday and is believed to have flown to the Yemen on Saturday, police said. His current whereabouts are unknown.
Mr Abdulhak and Miss Vik Magnussen both studied at Regents Business School in Regents Park, central London.
He is of Yemeni nationality and has been resident in London since he was a child.
Miss Vik Magnussen was last seen leaving the members-only bar, Maddox club, in Mayfair, central London, on Friday morning.
Post-mortem tests have revealed that she had sustained significant injuries to her neck. Further examinations are being conducted on her body to find out the exact cause of death.
Det Ch Insp Jessica Wadsworth said: "We wish to interview Mr Abdulhak as a matter of urgency to further investigate what happened to Martine in her final hours and how her death came about."
She added: "The overwhelming support and condolences being received by Martine's family are testament to the number of lives she touched."
Ms Vik Magnussen moved to London in February last year when she began studying business at the school.
Her parents, brother and sister have flown to the UK from Norway.
No arrests have been made.