One Mexico shooting has occurred in a cockfighting pit in Michoacan state, with authorities saying that at least 20 people have been killed and several others wounded.

Authorities described the Mexico shooting incident as one of the deadliest attacks in recent years, according to an Aljazeera report.

The details of the motive behind the attack were not immediately released. Local media reports noted that gunmen stormed a cockfighting pit and shot at the attendees.

President Andres Manuel Lopez Obrador said that it was a massacre of one group by another, expressing his regret at the deaths.

Lopez Obrador blamed criminal gangs for the shooting, adding that a team was dispatched to investigate the Mexico shooting incident.

Violent attacks on gatherings of rivals have become increasingly usual.

Gunmen in various areas of Mexico have attacked funerals and wakes, as well as bars and clubs in attempt to take out as many of their rivals at one time, according to a BBC News report.

Forensic experts noted that all the victims in Las Tinajas were 17 men and three women.

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Michoacan State Violence

Michoacan has taken the brunt of the drug war when then President Felipe Calderon's fight against drugs and traffickers started in December 2006, according to a Reuters report. Calderon sent in some 5,000 troops into the state, focusing on Apatzingan.

Two years after, the military arrested a suspected La Familia cartel boss Alberto Espinoza Barron.

In May 2009, 27 public officials in Michoacan, including 10 mayors, are arrested and accused of having connections with the drug trafficking industry.

It was the biggest coordinated crackdown on elected officials during Calderon's drug war. However, judges threw out the charges in 2010.

Activists from Michoacan clamored for the government to fight all drug cartels equally and return land to an estimated 35,000 people displaced by fighting.

Hipolito Mora, a founder and former leader of the 2013-2014 vigilante self-defense movement, noted that the place is worse than ever in terms of safety, according to an ABC News report.

Mora said that a group of activists met with senior government officials and told them that "they have to fight all the cartels, not just one."

In addition, the group demanded the authorities take into account the advice and opinions of Michoacan residents in creating a new strategy.

Rev. Gregorio López said that drug cartels now essentially control parts of the state. López is a priest once known for wearing a flak vest while celebrating mass, according to an ABC News report.

López said that at least 35,000 people have been forced to flee their homes and farms in recent years, adding that the government should return their land and reimburse their losses.

The priest noted that warring drug cartels extort money from almost all merchandise passing through Michoacan.

Michoacan's armed civilian "self-defense" vigilante movement lasted from 2013 to 2014. However, many vigilante forces were later infiltrated by the cartels.

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This article is owned by Latin Post.

Written by: Mary Webber

WATCH: Cartel violence leaves a trail of ghost towns in Mexico - from Al Jazeera English