Firefighters are still working on dousing a three-alarm fire at a commercial building in Etobicoke.

The fire broke out at a cardboard factory at 450 Evans Ave., near Kipling Avenue, at around 11 a.m. on Friday.

It started in the corrugation machine, involving a number of motors and a large conveyor belt, and spread into the duct work, which has paper fibres in it.

Toronto Fire officials said four workers who tried to extinguish the fire had minor smoke inhalation and were taken to hospital as a precaution.

Officials have estimated the damage at $500,000.

The Ontario Fire Marshal’s office has been notified, as well as the Ministry of Labour due to the workers’ injuries.

Police have closed Evans from Wickman Road to Treeview Drive.