Colombia beat Uruguay 1-0 in Wednesday's Copa America semi-final despite playing the second half with only 10 men to set up a title decider against defending champions Argentina, before the night descended into chaos as players clashed with fans.
The semi-final in Charlotte, North Carolina ended with Uruguayan players confronting Colombian fans in the stands as security personnel struggled to restore order.
South American governing body CONMEBOL said it was investigating the incident, as per Reuters reports.
While the majority of the 70,000-plus crowd cheered on Colombia from the start, Jefferson Lerma scored the winner after Uruguay forward Darwin Nunez missed three good opportunities to put his side ahead.
The Liverpool striker had a great chance in the box in the 17th minute but curled his effort inches wide before a scuffed shot and another curling strike failed to find the target as he sat on his haunches wondering how he had missed.
Uruguay were made to pay for those missed chances when Lerma rose above the defence at a corner and squeezed his header past goalkeeper Sergio Rochet as James Rodriguez claimed his sixth assist of the tournament.
However, the game took a turn in first-half stoppaget time when Colombia right back Daniel Munoz elbowed Manuel Ugarte in the chest when play was stopped and picked up a second booking.
With Uruguay dominating possession in the second half, manager Marcelo Bielsa threw on Luis Suarez in the 67th minute and the veteran striker nearly scored moments later, the 37-year-old's shot hitting the post as he sank to his knees in frustration.
Colombia had a golden opportunity to seal the win in the 88th minute when they won the ball back in Uruguay's box but Mateus Uribe sent his low shot wide.
Colombia fans were left in disbelief when Uribe saw another shot deflect off the keeper and cannon off the crossbar in added time.
Despite those misses Colombia held on for victory, extending their unbeaten run to a national record 28 games and reaching their first final since 2001 when they won their only title.
They face Lionel Messi's Argentina in Florida on Sunday while Uruguay stay in Charlotte for the third-place playoff against Canada on Saturday. It is Uruguay's best Copa performance since their last title win in 2011.
After the game, videos showed what appeared to be Uruguay players wading into the stands to exchange blows with Colombia fans as police personnel tried to keep the two sides apart.