UPDATE: Firefighters have fully contained a 3-acre grass fire that was sparked by lightning near Waterton Canyon Tuesday afternoon. 

Crews worked until around 8:30 p.m. and returned in the morning to contain the fire.

Waterton Canyon in Jefferson County, west of Denver, was evacuated and closed to public access Tuesday as firefighters responded to a fire burning near the base of the canyon.

The small grass fire was burning south of Lockheed Martin, and at one point, was about the size of two football fields, according to West Metro Fire. No structures were threatened.

The fire was reported shortly before 2 p.m., and by 3:15 p.m., smoke was no longer visible from the command post staged near the fire, West Metro said.

About 50 firefighters and two helicopters responded to the scene. A drone with infrared capability is being used to find hotspots for hand crews on the ground. West Metro said the cause of the fire was lightning. Read more at 9news.com.