Police spokesman Steve Warneke said three males were stabbed, and a fourth may have been stabbed, but that person left the scene.
Police have several people in custody and are not currently looking for other suspects. None had been formally charged as of just after midnight.
Police say that the incident was called in at 9:55 p.m.
Warneke described the scene as "very chaotic." He said police did not yet know what led up to the fight or whether the men had attended the game.
The Denver Post reports there were multiple eye-witnesses.
Warneke said one person was initially in critical condition, but all are conscious and talking.
Stadium Management Company issued an email stating that it is working with authorities.
The Broncos lost 27-20 to the San Diego Chargers.
The stabbing Thursday is just one of several recent incidents involving football fans.
Earlier this month in Kansas City, Mo., a man died after an altercation in the Arrowhead Stadium parking lot during Kansas City's game against Denver.
In September in San Francisco, a teenage fan suffered a concussion and a broken arm and nose at Candlestick Park after police say he was attacked during the 49ers' game against Indianapolis.