Investigators are still trying to figure out what caused a fire that destroyed an east side Mexican restaurant early Saturday morning.

At about 4:45 a.m. a 911 call was made, reporting smoke coming from Guadalajara Fiesta Grill, 750 N. Kolb Road between East Speedway and Broadway on the east side.

Firefighters arrived within minutes to find the restaurant’s attic engulfed in fire, with heavy smoke and flames coming from the roof.

“The crew pulled hose lines into the front door of the restaurant to search the building and find the fire,” said Capt. Barrett Baker, a spokesman for the Tucson Fire Department. “The smoke was banked down to knee level inhibiting visibility, but the firefighters reported cooler temperatures, indicating the fire was in the attic space above them.”

While one crew entered through a front door, a second crew entered from a door on the southeast corner of the restaurant in an area of the building closer to the smoke and flames, Baker said. The interior crew was able to pull down the ceiling to reveal the attic space engulfed in flames.

That’s when commanders decided to pull crews out of the building and off the roof and fight the fire defensively from exterior positions.

“They were making headway and all of the sudden things changed and they pulled everyone out and good thing they did because the attic was completely involved and once it got going, it got going fast,” Baker said.

Two alarms were dispatched to the scene with about 40 firefighters and 14 units responding.

The majority of the flames were extinguished within an hour, but crews continued to pour water on the building for several more hours to extinguish hot spots.

The restaurant sustained “heavy, heavy fire damage,” Baker said, and the building is a total loss.

A post Saturday afternoon on the Guadalajara Fiesta Grill Facebook page read, in part: “The building itself will require a great deal of work to repair and return to operational capacity. We will rebuild and we will reopen as soon as humanly possible.”

A former north side affiliate of Guadalajara Fiesta Grill is still closed for repairs after a fire in a storage room May 29.

Guadalajara Original Grill, 1220 E. Prince Road and North Mountain Avenue, suffered minimal damage when a fire started in a storage closet, but smoke caused heavy damage throughout the building.

The restaurant likely won’t open until late September, according to a post on the Guadalajara Original Grill Facebook page.

An accidental electrical malfunction was one of the theories considered by investigators looking into the Guadalajara Original Grill fire, but the cause eventually was deemed undetermined, said Capt. Chris Jurvig, a TFD spokesman, who estimated the damage at the time of the fire at $200,000.

“Although we are no longer associated with Guadalajara Fiesta Grill on Kolb Road we are deeply saddened by their loss. We wish them the best in their rebuilding,” read a post on the Guadalajara Original Grill Facebook page Saturday.