Windsor Fire and Rescue says damage to an apartment building in the 1200-block of Wyandotte St. E is pegged at $300,000.
The incident happened Saturday, and the Ontario Fire Marshal's been in town investigating the scene since.
Another Saturday blaze, just two blocks away on Wyandotte St. E, had also been ruled arson. There's no word on damages in that fire.
No one was hurt in either incident.