A brush fire sparked that Wednesday night just south of the United States-Mexico border spread into U.S. territory Thursday morning, Cal Fire San Diego said.
The fire, dubbed the Copper Fire by the agency, started near the base of Otay Mountain south of the border Wednesday night and grew to about 5 acres within an hour.
Cal Fire firefighters sent a large response in case the fire's spread across border as Mexican fire crews tackled the blaze from the south overnight.
At 6 a.m. Thursday, Cal Fire said at least 50 acres on the U.S. side had burned, the agency said. Within 20 minutes, the fire's activity decreased, allowing crews to make progress in the firefight.
The spread into the U.S. was halted a short time later. Smoke may still be visible but Cal Fire said the blaze was not a threat.
The fire was first reported by Border Patrol at around 10:15 p.m., during a Red Flag Warning that wasn't set to expire until 6 p.m. Thursday.
No other information was available.
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