A brush fire started near Ramona shortly after noon on Monday by sparks from a metal-grinding tool, according to a Cal Fire San Diego spokesperson.
A large plume of smoke from the blaze, which was burning near the 14000 block of Fernbrook Drive, was visible for miles around. The fire burned four acres, according to Cal Fire, before crews and water drops and fire-retardant drops from the air allowed crews to quickly gain control of the vegetation fire.
Cal Fire spokesperson Thomas Shoots said the fire was started by a spark that went into brush from an angle grinder, which was being used on metal.
At least one structure in the area was threatened by the flames, which burned in an area with heavy fuels, officials said.
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Although the fire was slow-moving, there were gusts of wind up to 19 mph in the area, according to San Diego Gas & Electric, which could have made the fire difficult to fight if it had not been stopped quickly.
Damage from the flames was limited to a single hillside. No structures were affected, according to Cal Fire.
Cal Fire officials said later in the afternoon that they had determined that the fire was caused by "angle grinding" of metal, which shot some sparks into nearby brush.