A blaze that devastated a heritage-listed, derelict mansion in Christchurch is being treated as suspicious.
About 50 houses were evacuated yesterday evening after the historic Antonio Hall on Riccarton Rd caught fire, sparking road closures and severe traffic congestion.
At least 50 firefighters were at the category 2 heritage-listed building at the height of the blaze.
Nobody was found to have been in the building.
Firefighters contained the blaze about 8.15am and managed to save the chapel from fire.
Evacuated residents were able to return shortly after.
A small crew remained at the scene overnight to dampen hotspots, and would remain there today.
A Fire and Emergency spokeswoman this morning said the fire was being treated as suspicious and investigators would return to the scene this morning.
"The investigation is expected to take some time due to the size of the building and unsafe nature of some parts of the structure."
All road closures had been lifted in the area.
The property boasts nearly 300 rooms and was once used as a Catholic seminary. It is understood the hall was unoccupied at the time of the fire.
Christchurch Heritage Trust chairwoman Dr Anna Crighton said "decades of neglect" was to blame for the devastating fire.
The building was not being looked after, and was a well-known spot for squatters and parties.
The building was locked up and sitting there for about 20 years, with nothing being done to it, and had slowly disintegrated through neglect.
Heritage buildings were part of New Zealand's cultural history, and needed more protection from irresponsible owners, she said.
Hobby photographer Vishal Makwana said he was in the building last month and parts of it were still in good condition. He said the church section was well taken care of by a group of volunteers.
Other parts of the mansion were off-limits because of earthquake damage, and some buildings had fallen into disrepair.
Photographs he took at the time show graffiti-covered walls, curling wallpaper, and vines growing across the ceilings and walls.