Fire and Emergency investigate suspicious fire in abandoned Wellington building

A fire at the old 'Boys Institute' in Wellington overnight is being treated as suspicious.

Emergency services were called to the abandoned building on Tasman Street, Mount Cook, at 12.23am.

Fire and Emergency shift manager Murray Dunbar said first responders initially feared the building may have been inhabited by squatters, but a later search found it empty and no injuries were reported.

Most of the Boys Institute complex was demolished in 2008, and the front building and facade, which remained, had been "totally destroyed" by the fire, Dunbar said.

It had since been extinguished, though firefighters remained on stand-by in case of hotspots.

The building remained cordoned off and would be examined by police and specialist fire investigators.

Five pumping and two aerial appliances attended the blaze, along with three support vehicles.

There were also some concerns about the brick and concrete building's structural integrity, particularly that the roof may collapse, Dunbar said.

The Boys' Institute began as a subsidiary of the YMCA but started to operate as a separate entity in 1892. Construction on the Tasman Street buildings began in 1914.