An explosive wildfire has nearly tripled in size overnight in Northern California and prompted closure of a major freeway, just weeks after a nearby blaze that left neighborhoods in ruins and killed eight people, officials said Thursday. The fire that erupted Wednesday afternoon and devoured timber and brush on both sides of Interstate 5 near the Oregon state line had expanded to 23 square miles Thursday, prompting mandatory evacuations, the U.S. Forest Service said in a statement. That’s up from 8 square miles burning Wednesday.

Authorities said Thursday night that 45 miles of I-5 will remain closed until at least Friday morning. The highway runs north from the Mexico border through California, Oregon and Washington state to the border with Canada. The California Highway Patrol said the closure in Shasta County has significantly snarled traffic. The agency warns motorists and truckers to avoid the region if possible.

CHP officer Jason Morton said the only alternate route around the closure is taking motorists up to eight hours to navigate. Morton said the 140-mile detour on Highway 299 to Route 89 has been bumper-to-bumper the entire route. He said the winding, mountain roads funnel to one lane each way at many points, and traffic often slows to 1 mph. Morton said officials will reassess the safety of reopening Interstate 5 on Friday morning.

The scattered homes and cabins in and around Shasta-Trinity National Forest were under evacuation orders, from the community of Lakehead north to the Siskiyou County line, said Chris Losi, a spokesman for the forest. “It isn’t a lot of people,” he said.

Officials said the blaze was human-caused, but they did not indicate whether it was arson or an accident.

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