Up to 17 fans have been reported dead, with 22 injured, after violence broke out during a game between Mexican football teams Queretaro and Atlas.
A brawl broke out at Queretaro's Estadio Corregidora on Saturday as the rivals faced off, with officials stopping play in the 62nd minute as supporters of reigning champions Atlas clashed with those of their opponents..
Fan violence spilled onto the field forcing the Liga MX contest at Estadio Corregidora to be abandoned midway through the second half, with at least 22 people thought to have been injured.
While some players left the pitch amid the scenes, others stayed out on the field in an effort to calm tensions between the rival groups of supporters.
Other matches continued on Saturday despite the violence, before all of Sunday's fixtures were suspended.
Mexican football authorities and both clubs condemned the violence, promising full investigations.
"The Mexican Football Federation regrets and condemns the events that occurred this afternoon at Estadio Corregidora in Queretaro, in the match between Queretaro and Atlas," read a Mexican Football Federation statement.
"Football must be a space of healthy coexistence where any type of violence is inadmissible.
"The FMF will monitor and assist in the investigation process with the corresponding instances so that those responsible are sanctioned in an exemplary manner."
Liga MX president Mikel Arriola insisted any breakdown in stadium security would be investigated swiftly.
"Those responsible for the lack of security in the stadium will be punished in an exemplary manner," Arriola posted on Twitter.
"The safety of our players and fans is a priority."
Queretaro insisted they would cooperate fully with all investigations.
"We roundly condemn the events that occurred at Estadio Corregidora," read a club statement.
"We are in full communication and coordination with the authorities so that they can act quickly against anyone responsible.
"As an institution we condemn violence of any kind."
TV Azteca broadcaster David Medrano Felix tweeted after the game, claiming an "unofficial" tally of 17 deaths, though at the time of writing this figure remains unconfirmed. Different sources carry different numbers of deaths and injuries, with The Mail reporting that two had died with a number of those injured in critical condition.
Former Mexico and Bolton Wanderers striker Jared Borgetti, who now covers the sport for ESPN, responded to the violence as footage from Queretaro continued to circulate.
"Who told them to go to the stadium, sing and get mad at their team for not playing well or winning. And what to say against the rival simply for wearing the opponent's shirt," Borgetti said.
"THESE ARE NOT FANS!! Soccer is a sport to go to have fun not to get angry."
Atlas echoed the calls from their opponents, insisting football must be able to promote family values.
"Atlas FC regrets and disapproves of the events that took place in Estadio Corregidora," read the Atlas statement.
"Soccer must be an ally to promote values and fun for the whole family.
"We request the pertinent authorities, the Liga BBVA MX and the FMF, to investigate thoroughly and reach the ultimate consequences, determining the responsibilities of those who are involved, and applying the full force of the law."