It was around 7:51 p.m. this Saturday when the 9-1-1 Emergency System received the report of firearm detonations in the bar located in the neighborhood of December 12.
After the report, security personnel moved to the area, where paramedics confirmed the death of six men and six women.
The authority indicated that a search operation was immediately launched to locate the alleged perpetrators.
The Secretary of National Defense, the National Guard and the Attorney General of the State of Guanajuato are working together with local authorities to restore order tonight.
During the attack three other people were injured.
On September 22, an attack at another bar, also in Guanajuato, left 10 people dead.
Guanajuato has occupied the first places in the national homicide rankings for several years.
At least two groups, the Jalisco New Generation Cartel and the Santa Rosa de Lima Cartel are fighting over their territories.