Fire and Emergency NZ assistant area commander Michael Dombroski said an alarm was set off at 2am after a blaze erupted in a switchboard in the hospital's plant room on the eighth floor.
Eleven fire crews headed to the central Wellington hospital but Dombroski said the fire was contained by the internal sprinkler system and had been partially extinguished by the time first crews arrived.
Firefighters, carrying equipment up eight floors to reach the burning room, put the fire out but a massive salvage operation followed after significant amounts of water cascaded down into the lower levels of the block.
"There's a significant amount of water damage which decreased as you went down," Dombroski said. "It even went down to level one where there was a puddle. From eight, seven, six it's quite significant where damage has been done."
The blaze had been contained to a single switchboard about the size of a door, but the rest of the floor also has serious smoke damage.
He said an alarm was set off at 2am after a blaze erupted in a switchboard in the hospital's plant room on the eighth floor.
The hospital's director of provider services Joy Farley said the cause of the blaze was being investigated but was thought to be electrical.
"A team will remain on site to assess and address any further damage over the next 24 hours," said Farley.
"Our operations are expected to function as per normal."
There had been no reported injuries.
Dombroski said the fire was contained to the room by the internal sprinkler system and had been partially extinguished by the time first crews arrived.
Firefighters, carrying equipment up eight floors to reach the burning room, put the fire out but were left with a massive salvage operation after significant amounts of water cascaded down into the lower levels of the block.
He said it was a labour-intensive, resource-intensive operation to get one hose line working to fight the blaze.
Fire crews remained at the hospital for four hours.
"There's a significant amount of water damage which decreased as you went down. It even went down to level one where there was a puddle. From eight, seven, six it's quite significant where damage has been done."
Fire investigators would be returning to the hospital today to probe the cause of the blaze.