DENVER – Firefighters extinguished a blaze that torched several rows of seats and a suite area at the Denver Broncos' stadium on Thursday.

The fire broke out in the third-level seating area at Empower Field at Mile High just after 2 p.m. and burned at least six rows in two sections. Firefighters quickly brought the blaze under control but were trying to determine whether it had spread to other areas of the football stadium, which seats 76,125 people.

About 100 people were attending an event on the second level, but the stadium was otherwise empty. No injuries were reported.

Footage from a news helicopter showed several firefighters using hoses to extinguish the blaze, which sent a large plume of black smoke billowing out of the stadium near downtown Denver. The Denver Fire Department tweeted several photos showing large flames spreading through the seating area.

Capt. Greg Pixley, a spokesman for the fire department, said it appears the fire originated in the suite and spread to the seats, which are made of plastic.

“This type of plastic that the seats are composed of burns with not only significant ferocity ... but also produces a tremendous amount of black smoke,” he said.

Investigators have not said what caused the fire.