Police hope advances in DNA testing will one day provide more answers to the unsolved murder of Japanese tourist Kayo Matsuzawa.

Her badly decomposing body was found locked in a fire-alarm cupboard in the Centrecourt building in Queen St, Auckland, on September 22, 1998.

Ms Matsuzawa, 29, disappeared after checking into the Queen Street Backpackers Hostel in Fort St on September 11, and the last sighting of her was at the hostel the following day.

The inquiry head, Detective Inspector Kevin Baker, said no significant information had been received in the past few years.

Police were keeping "several exhibits" they fear could be destroyed by forensic testing.

"They are very small and at this point of time we'd prefer to hold those back until we feel comfortable we can put them forward and gain some benefit from their examination," Mr Baker said.

Police hunting the killer had been interested in "a number of people", including a Russian man who stayed at the same hostel and suddenly left the country the day after Ms Matsuzawa's body was found.

Mr Baker said the man was interviewed when he returned to New Zealand 2 1/2 years after the murder and police were "satisfied he was not involved".

They had also looked at sexual assaults where the victims were drugged, although it is not known if this happened to Ms Matsuzawa.

Mr Baker said it was always possible someone would come forward with information.