Colorado's Empower Field at Mile High, the home of the Denver Broncos, briefly caught fire this afternoon before it was contained and put out by the Denver Fire Department, officials said.

The fire department tweeted that firefighters arrived to thick, black smoke coming from plastic seats that were on fire near the stadium's suite area and on the third-level seating area.

Officials said after the fire was contained that it was estimated to have burned over approximately 1,000 square feet and that the cause was unknown at the time, according to KMGH-TV in Denver. The stadium was empty except for an event on the second level attended by about 100 people who were all evacuated safely.

A video from an individual who was inside on a tour of the stadium showed one seat on fire as an origin point for the larger fire, but it is still unclear how it started, Ivan Rodriguez of KMGH tweeted.

"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," according to a post on the stadium's Twitter account. "That area of the stadium was quickly evacuated as a precaution and there were no injuries sustained."

Fire department public information officer Greg Pixley told reporters that a sprinkler system was set off by the smoke and helped keep the fire "in check" until the department could arrive, KMGH added.

"The sprinklers were working... but the significance of a fire like this, with the amount of petroleum products [the seats] burning, creates significant heat," Pixley said. "Those sprinklers did as best as they could and our firefighters were able to place hose lines to reduce the amount of damage."

Around 3 p.m. local time (5 p.m. ET), Pixley said the fire had been contained and investigators were working to make sure it didn't spread anywhere else and to determine whether the fire could have potentially led to structural damage to the stadium.

Seventy-five firefighters responded to the scene to combat the fire, which was seen by people around the city as the black smoke poured out of the stadium. Dozens of photos and videos were posted to Twitter as many people questioned what was happening inside the stadium or where the fire was coming from.

The 76,125 seat stadium opened in August 2001 and was built to replace the original Mile High Stadium, which served as the home of the Broncos from 1960 to 2000.

Update 03/24/22, 6:55 p.m. ET: This story was updated with additional information.

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