Three fire crews were called to a fire at a former dairy in the Whanganui suburb of Castlecliff on Sunday morning.
A Fire and Emergency NZ (Fenz) spokeswoman said they were notified about 7.15am.
“We got multiple calls to a building on fire, one that was reported to be no longer in use.
“When we arrived, it was well involved.
She said because the building was empty, police and a fire investigator were also at the scene to find out what caused the fire.
A police spokesperson said they assisted with traffic management.
The building, on the corner of Mosston and Heads roads, was formerly the Balgownie store.
Two fire crews were still at the scene at 8.30am but the fire had been extinguished.
The fire investigator finished the scene examination on Sunday, but the investigation was continuing so it was too early to comment on a possible cause, Fenz said.