[1] Mexican officials stated that 49 people were decapitated and mutilated by members of Los Zetas drug cartel and dumped by a roadside near the city of Cadereyta Jiménez in northern Mexico.

[4] The bodies were found in the town of San Juan in the municipality of Cadereyta Jiménez, Nuevo León at about 4 a.m. on a non-toll highway leading to Reynosa, Tamaulipas.

"[12] The cartels also fight for the control of local drug markets and extortion rackets, including shakedowns of migrants seeking to reach the United States.

[13] In addition, the discovery seems to echo several other mass murder events where the drug cartels have left large numbers of bodies in public places as warnings to their rivals.

[20] On the supply side, the increased pressures on Sinaloa kingpin Joaquín Guzmán Loera, whose operations in Colombia in 2012 prompted his organization to grab larger shares of cocaine from Peru and Ecuador, threatened the supply-lines of Los Zetas, and triggered tit-for-tat attacks among both cartels.

Surveys showed that voters thought that the Institutional Revolutionary Party (PRI), which ruled Mexico uninterruptedly from 1929 to 2000, is likely to control and put down the violence.

[25] The practices of beheading victims in Mexico is believed to have come from Guatemala in the year 2000, when Los Zetas extended their criminal network into Central America and eventually incorporated with the elite jungle military squad known as the Kaibiles.

[31] Two trucks containing 35 dead bodies were found at an underpass near a shopping mall in Boca del Río,[32] having reportedly been abandoned there by armed men in the middle of the highway.

[48] At 07:00 hours, another burning vehicle was discovered in the northern city limits of Culiacán, inside which were four bodies handcuffed and clad in bulletproof vests.

[53] Dismembered remains of 14 men were found in several plastic bags inside two vehicles in the border city of Nuevo Laredo, Tamaulipas, on 17 April 2012.

[62][63] The decapitated bodies were found with a message allegedly signed by Joaquín Guzmán Loera, demanding recognition presence of the Sinaloa cartel in the area.

[68] In 2012, the state of Nuevo León and its surrounding territories have become a battleground for a brutal conflict between Los Zetas and the Gulf Cartel, two drug trafficking organizations from northeastern Mexico.

The municipality of Cadereyta Jiménez – a middle-class, industrial community where the bodies were found – is known for its broom factory, an oil refinery, and its historical role as one of the first places where baseball was played in Mexico.

[70] Nonetheless, it had at least five municipal employees slain in April 2012; just a week before the massacre, a military general stepped up and took over the city's depleted police force.

[72] Initially, the Mexican authorities reported the discovery of 37 bodies early in the morning on 13 May 2012 in the town of San Juan, 75 miles (125 km) southwest of the border city of Roma, Texas.

[81] Nonetheless, the victims are believed to be more than 25 years of age,[82] and many of them had tattoos of the Santa Muerte ("Holy Death") – a female skeletal grim reaper – which could facilitate their identification.

[77] The bodies were taken to the hospital in the University of Monterrey for DNA testing and further investigation;[9][83] dozens of military men were ordered to guard the surrounding area.

[83] Nuevo León's security spokesman said that the 49 people were killed up to 48 hours earlier at a different location, most likely in the neighboring state of Tamaulipas,[84] and then transported by truck to where they were found.

"[90] El Salvador asked Mexico for the DNA results of the victims in Cadereyta to make sure if those killed were migrants from their country,[91] but as of July 2012, none of the bodies have been identified.

[94] The Attorney General of Mexico (PGR) attributed the escalating violence in the country to the criminal organizations headed by Joaquín Guzmán Loera (a.k.a.

[100] A Blog del Narco article on 15 May 2012 pointed to a video recording uploaded on YouTube showing several members of Los Zetas disposing of the butchered bodies on the highway in Cadereyta.

"[102] Alongside the bodies, they placed a banner: "This is going to happen to all the Gulf and Sinaloa cartel members; the Mexican marines; Federal police; and government forces.

"[101]On 15 May 2012 Los Zetas allegedly put up five narco-banners from bridges or in other public places of San Luis Potosí and Zacatecas[103] denying responsibility for the Cadereyta Jiménez massacre.

[105][106] In the written banners, Los Zetas disassociated themselves from the slaughter in Nuevo León, and asked the Mexican federal government to conduct an investigation before blaming them.

[113] Officials of the Secretariat of National Defense stated that the cartel members were captured during a military operation in the area in which cocaine was allegedly seized.

[115] The massacre was viewed as an attempt by the Gulf Cartel to stoke law enforcement crackdown in Los Zetas territory – a tactic known as "heating up the plaza.

[118] In Guadalupe, Nuevo León on 18 May 2012, the operation led to the capture of Jesús Daniel Elizondo Ramírez, nicknamed El Loco (English: "The Crazy One"), a member of the Los Zetas.

[122] The bodies were transported from Los Herrera to Cadereyta, two municipalities between the city of Monterrey and the Rio Grande, and then dumped on the highway by Elizondo and 30 other gunmen.

[128] In the city of Santa Catarina, Nuevo León, the Mexican Navy arrested José Ricardo Barajas López on 3 August 2012, another cartel member responsible for the massacre.

[129] According to the Mexican authorities, Barajas López delivered the 49 alleged Gulf Cartel members to a man known as Tula, who forward the victims to Rolando Fernando Sánchez González, a former policeman and the regional boss of Los Zetas in Santa Catarina, for execution.