A building fire on El Camino Real in Palo Alto late Thursday night took firefighters several hours to fully extinguish because the fire was smoldering inside one of the walls.

The Feb. 24 blaze at the corner of El Camino Real and Margarita Avenue was reported around 11:30 p.m. and wasn't cleared by emergency responders until 3:06 a.m. on Friday morning, according to PulsePoint, an app that displays emergency response incidents.

When crews arrived at the site, they found a fire burning inside the back wall of a building that had gone up to the roof, Battalion Chief Ryan Stoddard said. The initial flames were quickly extinguished, but it was difficult to access the smoldering fire inside the wall, Stoddard said.

"It probably had been smoldering inside the wall for many hours and then finally grew large enough to show some smoke and flame," he said.

The older commercial building — home to a massage parlor and smoke and vapor shop — is made of stucco, brick and other masonry, Stoddard said. Firefighters used saws and sledgehammers to tear open the back wall.

No injuries were reported and the fire didn't reach the inside of the building. Lanes were closed in the area while emergency crews responded.

The cause of the blaze is under investigation, according to Stoddard. He added that it either started externally or inside the wall itself, pointing to the possibility of an electrical fire or the fire being related to asphalt that had recently been redone outside the building.