The fire was started around 2:15 p.m. in the northeast corner of the stadium, between sections 331 and 334.
Denver Fire said they believe the fire started on a fourth-level suite and spread to the seats below it on the third level.
The section of seats destroyed is located under the John Lynch, Jason Elam, and Champ Bailey banners.
In total, Denver Fire said the fire covered about 1,000 square feet of area, but the sprinkler system in the building was working and helped prevent its spread and extinguish the flames.
Fire investigators are working to determine what caused the fire.