The Apple fire had burned 26,450 acres by Monday morning and was at 5% containment.
The fire is spreading primarily to the north and east into the San Gorgonio Wilderness, San Bernardino National Forest authorities said in a statement.
New firefighting crews were dispatched to relieve crews that have battled the fire since Friday afternoon.
One home and two outbuildings have burned.
One minor injury to a firefighter was reported. The firefighter was treated and released back to duty.
In regard to control lines, “The fire is 5% contained, which is the area directly above Cherry Canyon on the southwest portion of the perimeter,” authorities said in an email to the Record Gazette. “The southern and southeastern area of Banning Ranch is looking very good. Control lines are in place, but will not be considered contained until the work on the line is complete, which should be complete in the next day or two.”
Fire activity is being driven primarily by record low moisture content of the vegetation combined with high temperatures and low relative humidity, which has contributed to active fire behavior both day and night.
Much of the area in flames is inaccessible by ground crews.
“Sunday night and early Monday morning the fire was very active. Multiple spot fires erupted on the north side of the perimeter. Two of the spot fires were caught but one grew significantly and will be assessed today,” authorities said.
Gov.Gavin Newsom’s office announced the state has secured a fire-management assistance grant from the Federal Emergency Management Agency to help cover costs for fighting the fire.
The amount of the grant was not immediately known.