One person was taken to hospital after being treated by paramedics following the fire.
Emergency services were called to Christchurch Radiators, a commercial building on Buchan St in Sydenham about 11.40am.
Two fire crews battled the blaze, which caused plumes of white smoke to billow from the roof, and could be seen across the city.
Fire and Emergency NZ senior station officer Mark Shaw said the blaze appeared to have started somewhere within the roof space.
Shaw said the building contained dangerous goods and combustible gas, which prompted the evacuation of nearby buildings.
“We did have some highly explosive oxy-acetylene cylinders and some LPG gas cylinders, so we evacuated people well back from the incident until they were contained,” he said.
“Now the evacuations have been eased to allow people back into their workplaces.
“It was just compressed gases and cylinders and none of it was compromised.”
He said it wasn’t clear how many people were inside the building at the time but one person was taken from the building and was receiving treatment.
-With NZ Herald