FAIRFAX (CBS SF) — Firefighters were battling a small vegetation fire at a remote location in the Cascade Canyon Open Space Preserve near Fairfax on Wednesday evening.

The blaze was reported at 4:21 p.m. off the Wagon Wheel trail, near Blue Ridge Fire Road.

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Around 6:15 p.m. the fire was estimated at two acres in size with about 80 firefighters on the scene. They accessed the blaze by ground as well as with assistance from a Cal Fire helicopter.

Cal Fire air tankers have also assisted by dropping fire retardant.

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“We expect to be on this at least six hours,” Marin County Fire Department Deputy Chief Mark Brown said in a statement. “We will augment staff and people will stay overnight to completely mop it up tomorrow.”

No injuries have been reported and no structures are currently threatened due to the fire’s location. The cause remains undetermined, firefighters said.

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Fairfax-Bolinas Road has been closed at Meadow Club Road.