A fire broke out Tuesday at a garage or shed behind a home in the Mountain View area.
The blaze was reported at about 7:45 a.m. behind a home in the 700 block of South 45th Street, according to the San Diego Fire and Rescue Department.
It was unclear what sparked the fire, but fire crews said squatters were living in the back of the unoccupied house. Two people who were seen running from the house were detained and later released, fire officials said.
Crews from San Diego and the National City Fire Department were working the scene roughly two hours later to fully knock down the blaze.
No injuries were reported.