Violence began in the parking lot Wednesday night when fans from two rival Mexican soccer teams – Chivas and Club America – arrived at Sam Boyd Stadium.
The Las Vegas Review-Journal reports fans threw rocks and bottles at each other before dozens of police officers moved in to quell the violence.
But the incident set the tone for the rest of the night, as unruly fans threw punches, tossed bottles and set off fireworks and flares during and after the match.
"It was probably the most surreal sporting event I have ever been to," said Adam Berchin, a freelance writer who covered the game for The Associated Press.
Berchin said a scuffle broke out between the two teams halfway into the game, after two players got into a shoving match on the field.
"In no time both sides were all in one massive scrum," Berchin said.
He and AP freelance photographer David Becker said during the match flares were thrown onto the field and fireworks were being set off in the stands.
Chivas scored a goal late in the match but play was stopped with minutes left and time was allowed to expire when fans stormed the field. Chivas won, 1-0
More pandemonium broke out.
As the players left, "there was just an onslaught of people taking to the field," and brawls broke out between the yellow-clad Club America fans and red-and-white cloaked Chivas backers, according to Becker.
He said he saw one fan bloodied in the face.
"There were three police officers who picked him up and carried him away," he said.
"Nothing good came out of this," Club America President Ricardo Pelaez said after the match. "Security and soccer wise, we're going to rethink what we do in the future real hard."
Las Vegas police on Thursday said any updates about or injuries would come through the department's public information office, which was closed because of the July Fourth holiday.