(CNN) Flames burned Thursday in a construction zone on the third level at Empower Field at Mile High stadium in Denver, the city's fire department said in a tweet. No injuries were reported.
"A small fire that occurred in a construction zone near the East Club Lounge at Empower Field at Mile High has been contained by @Denver_Fire. That area of the stadium was quickly evacuated as a precaution and there were no injuries sustained," Empower Field at Mile High said in a tweet.
The fire department posted several photos on Twitter showing large flames engulfing seats and thick black smoke at the home stadium of the Denver Broncos. Another shows gray smoke as water hits the fire.
Greg Pixley, a spokesperson for the Denver Fire Department, said it was a "significant fire" that burned what he estimated to be at least 1,000 square feet.
"Sprinklers attempted to stop the fire, but firefighters were needed to complete extinguishment. Heavy fire & smoke was found on our arrival," the Denver Fire Department said in a tweet.
CNN affiliate KCNC reported the smoke from the stadium could be seen for miles.
The cause of the fire is unknown, according to the fire department's Twitter feed.
Pixley said there was an event underway at the stadium but it was on the second level. He thought as many as 100 people might have been there.
The facility opened in 2001 next to the site of the previous arena named Mile High Stadium. It has undergone several name changes due to sponsorship deals and was renamed Empower Field at Mile High in 2019.
CNN has reached out to the Broncos for more information about the fire.
According to a schedule posted on the stadium's website, the next event at the facility is a monster truck show on April 23.