DENVER - More firefighters are headed to Rocky Mountain National Park to help fight a wildfire that has burned 400 acres.

The Fern Lake Fire started Tuesday around 2 p.m. and forced officials to close the Moraine Park campground as well as Upper Beaver Meadows and Bear Lake roads.

The fire burned actively from the time it started until Tuesday evening when it started to die down, said Larry Frederick, spokesman for Rocky Mountain National Park.

The fire is burning in alpine tundra about 2 miles west of the Fern Lake trailhead in Moraine Park.

"This is an area of very steep heavily wooded terrain with some beetle kill," Frederick said adding that the area has not burned since the 1500s.

Around 65 firefighters were on scene and about 120 personnel and seven fire engines are expected to be available to fight the fire on Thursday.

A heavy helitanker joined the fire suppression efforts Wednesday, but was called off in the afternoon due to high winds.  That helicopter and another helitanker are expected to be available Thursday for fire suppression efforts.

Weather conditions call for Wednesday's gusty westerly winds to diminish overnight.  Overnight temperatures are expected to be 25 to 30 degrees. No rain is forecast for the area of the fire through the end of the week.

So far there are no plans to evacuate residents.  Currently, Bear Lake Road, Upper Beaver Meadows Road and Moraine Park Campground are closed.  Trails west of Bear Lake Road and south of Trail Ridge Road are also closed.

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

The fire's cause is under investigation.

Due to fire conditions at Rocky Mountain National Park, smoking and open fires in the park’s backcountry are now prohibited.