Investigators are now labeling a fire at a north side Thunder Bay residence last week a case of arson.

The homeowners were not in the building on Machar Avenue when the fire broke out on Wednesday night. 

The office of the Fire Marshal has determined it was set deliberately, and Thunder Bay police have now begun a criminal investigation.

Police are asking anyone with information about any suspicious activity in the area the evening of March 6 to contact Crime Stoppers, which can be done anonymously.