Courtesy Northwest Fire

More than 40 firefighters battled a blaze that sent a Denny’s restaurant up in flames overnight.

Seven engine companies, two ladder companies and multiple support personnel from Northwest Fire, Mountain Vista Fire and Golder Ranch Fire responded to a 911 call just before 1 a.m. of smoke coming from the Denny’s at 5000 N. Oracle Road, on the northeast corner of West River Road and North Oracle Road.

The restaurant was open at the time of the fire's start, but the patrons had evacuated before emergency personnel arrived at the scene, according to Northwest Fire.

The two ladder companies used aerial master stream techniques in addition to the multiple hose lines positioned around the building, Northwest Fire said.

It took just under an hour for crews to extinguish the flames.

Investigators will not be able to determine the cause of the fire until the building is deemed safe to enter.