The blaze was reported at around 4:55 a.m. at a boarded-up two-story home at 2079 Altamont Road, Alameda County fire spokeswoman Aisha Knowles said.
It was the second time since last year that firefighters had responded to a blaze at the home, which was damaged by fire in November 2013, Knowles said.
The residence had been abandoned since that fire, and neighbors reported that squatters had occupied the house in recent weeks, Knowles said.
During this morning's response effort, a floor inside the home partially collapsed, sending one firefighter falling to a lower level, Knowles said.
The firefighter was not injured in the fall, she said. No other injuries were reported.
Burning embers started a spot fire on the roof of a neighboring home, but that fire was quickly extinguished and the blaze did not spread, Knowles said.
The cause remains under investigation.