ESTES PARK, Colo. - A wildfire had burned 300 acres in Rocky Mountain National Park by Tuesday evening.

Reported about 2 p.m., the wind-driven Fern Lake Fire caused the evacuation of Moraine Park campground and the closure of Upper Beaver Meadows and Bear Lake roads, park officials said. Moraine Park is an area where visitor view elk herds.

Trail Ridge Road remained open.

The blaze was burning up-slope toward toward alpine tundra and the Ute Trail, about 2 miles west of the Fern Lake trailhead in Moraine Park, said park spokesman Larry Fredrick. 

Gusting winds are driving the fire toward the east and north.

The fire is burning far from any structures, but there is concern it could reach the Moraine Park campground if it keeps moving east, Frederick said.

Callers tell 7NEWS the smoke is so thick it's ringing the sun and plumes are billowing over Estes Park.

Park firefighters and additional fire crews are on scene. But because of steep, inaccessible terrain, crews will not be put on the fire line tonight, Frederick said.

Fire crews will monitor the fire overnight and additional firefighters and engines are on order. The fire activity is expected to decrease during the night, he said.

A heavy helicopter and single-engine air tanker have arrived, but cloudy and turbulent conditions grounded the aircraft, Frederick said.

People can call a fire information number -- 970-586-1381 -- for a recorded message that will be updated as conditions change.

The fire's cause is under investigation.