A house four blocks south of Fresno State was severely damaged in an early morning attic fire Saturday.

Firefighters from Fresno and Clovis were dispatched to the blaze at 4768 North Jackson Avenue, said Fresno Fire Department battalion chief Randy Reitz. He said a neighbor reported the fire around 4:30 Saturday morning.

When Engine 6 arrived a few minutes later, its crew found a roof well-involved in flames. Reitz said firefighters made entry and discovered the residents weren’t home. They began attacking the fire and covering up belongings, he said.

Reitz said the fire fight then got complicated. “We had a propane tank explode, so firefighters had to exit the house. We then decided to use” a heavy water stream from the extended ladder of an ladder truck in front of the burning house “to knock down” the flames.

He said the fire spread throughout the attic. Sections of roof began collapsing, he added. “It’s common for attic fires to extend into hidden spaces inside the walls,” he said. “Firefighters will be here for several hours doing a tedious overhaul to make sure it’s out.”

The cause is undetermined, Reitz said. Because the residents weren’t home and there were no witnesses, firefighters have no information on what happened before the fire was reported. He said investigators will try to determine what probably started the blaze.

Reitz said firefighters from four engines and two ladder trucks, and two battalion chiefs were fighting the fire.

This was the second blaze in the neighborhood this week. A house a block away was destroyed in a fire early Monday morning. That fire was the second one at 4522 East San Gabriel Avenue in less than two months.