New Zealand police said Wednesday that a Wellington hostel blaze that killed at least six people was “suspicious”, revealing there was a separate couch fire two hours earlier inside the building.

“As part of our enquiries, we will be seeking to confirm any link between that couch fire and the subsequent fatal fire,” police inspector and acting district commander Dion Bennett said in a statement.

Police said the couch fire occurred two hours before flames and smoke engulfed the four-storey Loafers Lodge in the capital, and it had not been reported to emergency services at the time.

Many residents crawled through choking smoke to flee the fatal fire in the early hours of Tuesday, some of them plucked to safety from the roof.

Firefighters found six bodies inside the smouldering building, officers said, but they were unable to search everywhere because a roof had partially collapsed.

Police said they had now taken over the fire investigation and planned to enter the building for the first time on Wednesday when it is declared safe.

“This scene examination will be an extensive and methodical process and we expect it to take some time – likely several days,” Bennett said.

“Alongside the scene examination, officers will be working to locate and recover those who lost their lives in the fire.”

Bennett said he knew family, friends and fellow tenants were keen for news of those who were still missing.