The fire started at about 1:40 a.m. in the 600 block of South Bullis Road.
According to the Los Angeles County Sheriff's Department, a deputy found a man breaking through a wall with a shovel in order to rescue a woman trapped in a burning garage. The deputy removed some of the wooden sidings and pulled the woman to safety. She suffered burns over the majority of her body.
Two men who were also in the garage were able to get out before the exit was blocked by flames, authorities said. Both men were burned as well.
The deputy received minor burns to his right hand.
Investigators are still looking into the cause of the fire.