Police received a 911 call of a fire at 11:25 a.m. and notified the city's fire department.
Crews on scene reported fire through the roof of the building and an explosion as the blaze sent a large plume of smoke into the air.
The single-story structure housed a party rentals company that has been in business for a decade, according to its website.
There were no immediate reports of any injuries.
As a precaution, Glendale Water and Power shut off electricity service to 1,500 customers in the area. All service was later restored, according to the utility's website.
The cause of the fire is under investigation.
City News Service contributed to this report.