Police say a fire that destroyed a 70-year-old commercial building in Halifax is being investigated as arson.

Police and fire crews responded to the scene at 5426 Portland Place before 8 a.m. Sunday.

The blaze destroyed most of the property, which housed several businesses, including Ravensberg College, RCR Hospitality Group and National Art Limited.

More than 20 residents who live close to the building were forced to evacuate their homes after the fire, which left the brick outer walls of the building unstable.

Twelve townhomes were evacuated and residents have been told they could be out of their homes for up to two weeks.

The insurance company conducted the initial investigation after the scene was released by firefighters. Police have launched their own investigation after being informed of evidence to suggest arson.

"Now, given the state of the building and the scope of it, it was a very large building that was almost completely destroyed, so it is going to take some time for them to go through the rubble to see what they can find at the scene to lead us to the individual or individuals that may be responsible for setting it on fire," says Halifax Regional Police Const. Pierre Bourdages.

Anyone with information is asked to contact police.