Mexico President Andres Manuel Lopez Obrador is calling for an evaluation of justice and police officials in Guanajuato state, where gunmen killed 26 people and wounded five others at an unlicensed rehabilitation center.
Authorities said gunmen attacked the rehab center in the city of Irapuato in Guanajuato state on Wednesday.
A day after the attack, Lopez Obrador called on the opposition-led Guanajuato government to launch an investigation saying, "The problem (violence, murders and gang confrontations) grew a lot, they let it grow and we'll have to see if there is no criminal association between criminals and the authority."
Pedro Cortes, secretary of public security in Irapuato, said street-level drug dealers are known to seek shelter from drug gangs in the rehabilitation centers.
The attack occurred northwest of Mexico City in an area where the Jalisco cartel has been part of a violent turf battle.
The La Jornada newspaper said there have been four attacks since December on annexes in Irapuato, where people were abducted, some killed, and a building was set on fire.