The Fire Service is treating a fire in a building on Kilmore Street, Christchurch as suspicious.

Fire fighters were called to the scene around 5:30am and the small fire on the first floor of the building was quickly extinguished, southern fire communications shift manager Brent Dunn said.

A fire investigator remained at the scene to investigate a possible cause of the fire, however it was being treated as suspicious.

The fire in the commercial building at 55 Kilmore Street comes after two suspected arson on red-zoned properties in Christchurch yesterday morning.