An electrical problem is to blame for a fire at a west side duplex, San Antonio fire officials said.

The fire broke out a little after 6 a.m. on Monday in the 700 block of South San Augustine, near South General McMullen and Castroville Road.

The person who lives in the back part of the duplex -- where the fire occurred -- had left for work, officials said, so no one was home when the fire flared up.

The fire was contained to the back half of the building.