San Diego, CA – Neighbors were awakened in the wee hours of Thursday morning by the detonation of a natural-gas explosion.

Fire officials said the explosion took place at about 3 a.m. in the 11400 block of Menkar Place in Mira Mesa. Emergency operators, however, were not alerted to the situation until hours later.

“About 3 o’clock this morning, neighbors heard a large boom, but they didn’t know what it was,” Metro Arson Strike Team Capt. Paul O’Brien told NBC 7/39. “About 6:30 this morning, the fire department got a call for an extinguished fire.”

Responding fire crews determined that there had been an explosion in the attic area of the home. Damages caused by the explosion are believed to be a minimum of $150,000.

“It caused quite a significant amount of damage,” O’Brien said. “There’s a couple of walls that are blown up, and there’s some heat damage from it, where some curtains caught on fire.”

Investigators are still trying to track down the ignition source of the fire.

There were no residents in the house, which was for rent.