Sergeant Mark Gill, of Queenstown, said police had received information from friends of Mr Tornberg's ex-flatmate, who said they had spotted him in central Queenstown during the weekend.
It is understood the pair did not talk to Mr Tornberg.
Queenstown police had checked Mr Tornberg's bank transactions and cellphone records but it was not known if this information had helped in tracking him.
Mr Tornberg was reported missing on October 18, after friends and colleagues had not seen or heard from him.
He is described as 180cm tall, with blue eyes, and of medium build and was last seen at his Queenstown flat on October 6, wearing a black leather jacket, blue jeans and dark-coloured T-shirt.
"We just want to know where he is. It's an unusual disappearance.
"His friends say it's out of character for him not to be in contact," Detective Grant Miller, of Queenstown, said.
Mr Tornberg was not an outdoors enthusiast so it was unlikely he had gone tramping.
Nor had he left the country.
The Swede had a working holiday visa and had lived in Queenstown for about a year.
His next of kin in Sweden have been contacted and they also expressed concerns they had not had any contact from Mr Tornberg.
Anyone with information regarding Mr Tornberg is asked to contact Queenstown police, on (03) 441-1600.
