Mexico's first division referees and linesmen warmed up for their matches on Saturday wearing white shirts in protest at an attack on their chief by a club director.
Veracruz owner and president Fidel Kuri attacked Edgardo Codesal, head of the Mexican Football Federation (FMF) referees' commission, in the VIP box at his team's 3-1 home defeat by Leon on Friday.
Kuri, whose team are nicknamed Red Sharks, reacted to a 90th minute red card for Veracruz's Argentine winger Daniel "Keko" Villalva.
The white t-shirts worn by officials during the warm-up period at matches on Saturday bore the slogans "Security and Respect" on the front and the hashtags #FootballWithoutViolence and #MexicoWithoutViolence on the back.
The officials then changed into their normal shirts for the matches but wore white bands around the sleeves.
FMF regulations include a clause prohibiting players and fans from displaying political or social statements at matches but it does not include referees and linesmen, raising the question over whether the FMF would act against the protest.
Leon are the only team with maximum six points after two rounds of the Clausura championship -- before Sunday's matches when Toluca visit UNAM Pumas and Monterrey play at Puebla.
Title holders UANL Tigres, who lost their opening match 1-0 at Toluca, beat Morelia 2-0.
Tigres scored twice in less than two minutes late in the match through Javier Aquino and France striker Andre-Pierre Gignac, top scorer in the Apertura championship won by his team in the first half of the season, who hit the woodwork twice with earlier efforts.
Mexico City giants America, held 0-0 in a poor match against Puebla at the Azteca last weekend, beat Atlas 3-0 away in Guadalajara, holding out with 10 men for the last 22 minutes after their Ecuador midfielder Michael Arroyo was sent off.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)