But in the city of Fresno, vacant rarely means empty.
"We've had issues with the property over the last two months. We had multiple debris fires on the outside as recently as three weeks ago," said Battalion Chief Dennis Smith with Fresno County Fire.
[Ads /]
This time as firefighters entered the former warehouse, they found mattresses, personal belongings, and what appeared to be a bed. Squatting is not a new problem in the city.
But as the same buildings catch on fire repeatedly, dangers for firefighters grow.
"That creates an additional hazard because the structure is no longer in the same condition," said Robert Castillo with Fresno Fire. "The previous fire has weakened it."
The City of Fresno has seen a 28% increase in vacant structure fires this year.
[Ads /]
There's always a possibility that someone may be inside.
"Obviously it's boarded up. We are unable to see the true fire load and objects that may be burning," said Castillo.
The county is also seeing an increase in calls along the State Route 99 corridor.
Firefighters say as the anti-camping ordinance pushed transients outside city limits, it leads to more roadside fires and calls to homeless encampments.
Firefighters are working with property owners to put up signs, but they say neighbors also need to do their part and report suspicious activity.