UPDATE | 4:29 p.m. The fire east of Atascadero is now contained, according to Cal Fire.
Firefighters are still on the scene to make sure that all the hot spots are completely extinguished.
Authorities now estimate 25 acres of brush were burned.
Cal Fire crews from the Cuesta Conservation Camp were assigned to burn piles of brush along the Rocky Canyon Truck Trail, east of Atascadero, when one of the piles got out of control, officials said.
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The piles were being burned to reduce the overgrown vegetation in the area.
The fire did not threaten any structures, and no injuries were reported.
Original story: A brush fire east of Atascadero that's burned an estimated 50 acres is now about 65 percent contained, according to Cal Fire.
Reported at 12:33 p.m., the blaze began as a controlled burn by Cal Fire to get rid of weeds on Rocky Canyon Truck Trail, officials said.
About 80 firefighters are on the scene, which is about three miles north of Highway 58 along Highway 229 in the North County.
No structures are threatened and no injuries have been reported.