Investigators say an illegal campfire sparked a 2,143-acre blaze that prompted the evacuation of Southern California foothill homes last week.

San Bernardino National Forest spokeswoman Carol Underhill said Monday the campfire had likely been smoldering for a few days before winds blew its embers into the brush, sparking the wildfire on April 30.

The blaze on the outskirts of Rancho Cucamonga was 96 percent contained Monday night.

The fire, fanned by fierce winds, chewed through dry grass and chaparral, leading to evacuation orders for about 1,600 homes. No structures burned.

Anyone who may have seen hikers in the area last week is asked to call investigators.