The stairwell collapsed during the 2016 Kaikōura earthquake and the building has been sitting abandoned ever since.
A representative for the building’s owner, Prime Property, said the former office block was often targeted by squatters.
James Dunn said he had been through the building with police five times in the last three months, with trespass notices issued to 18 people.
He said Prime Property had taken extreme steps to stop people from accessing the building, including plywood, steel and temporary fencing. However, rough sleepers continued to break through the defences.
“I can show you a gate that’s probably got more reinforcing than a tank,” Dunn told media.
The building was so well fortified at ground level that responding firefighters had to cut a hole in the wall to access the injured man.
A spokesperson for Wellington Free Ambulance said it treated one person in a moderate condition.
They were taken to Wellington Hospital.
As the building is a magnet for rough sleepers, work is being undertaken to ensure no one else is at risk.
“Our main priority is that there is no other risk to life in there and that we take all care for our staff who are going to go in and assist as well,” Wilby said. “We are going to do a floor-by-floor search.”
