It was a blaze that triggered a response by nearly 700 firefighters from around the state, including hot shot crews, eight air tankers and five helicopters, said U.S. Forest Service spokesman John Miller.
"That's a considerable amount of air power for 350 acres," Miller said. "But when you look at the direction the fire was heading, it could have easily spread into Devore," he said.
The fire also shut down both directions of the 15 Freeway in the Cajon Pass due to the heavy smoke and flames.
The blaze, driven by mild winds, spread quickly through dry chaparral on the side of the northbound 15 near Kenwood Avenue starting at 10:55 a.m. Monday. Embers flew over the freeway, causing the blaze to continue off the southbound side.
Firefighters issued a mandatory evacuation of the Matthews Ranch area in Devore, but Miller said all the residents chose to stay. San Bernardino County firefighters stood by to protect structures in case the fire came too close.
The evacuation order was lifted Monday night.
The flames calmed down in the evening, giving firefighters a chance to get the fire fully contained. Firefighters expected to have the fire fully controlled by Thursday said U.S. Forest Service fire officials.
The freeway closure choked surface streets and brought traffic to a crawl on the main thoroughfare to and from the High Desert.
Most of the lanes were reopened by Tuesday morning, but Caltrans kept one southbound lane closed to repair a section of guardrail damaged by the blaze.
Fire investigators haven't determined a cause for the fire, but say the ignition source is very close to the freeway.
"Right now, we don't think it was nefarious in nature," Miller said.