Ten people, including a child, were killed when a riot erupted during family visiting hours at a prison in the northwestern Mexican state of Sinaloa on Thursday, Oct. 8, 2026, state authorities said. A second clash inside the same prison the next day, Friday, Oct. 9, left two more inmates dead, bringing the toll over two days to 12.
The violence broke out at the El Castillo Penitentiary in the port city of Mazatlan. The Sinaloa Public Security Secretariat described the incident on X as “a brawl occurred inside the prison facilities,” without detailing what set it off. State Attorney General Claudia Zulema Sánchez Kondo later said 17 people were injured.
Sinuhe Tellez, Sinaloa’s secretary of public security, said in a video posted on social media that “nine inmates and a minor who was visiting lost their lives, and 16 inmates were injured.”
Gunfire Heard Beyond the Perimeter
Local media reported that inmates used firearms during the fight. Witnesses heard several gunshots from inside the prison before the chaos began, N+ reported. Sánchez Kondo said ballistic evidence showed both a long gun and a short gun were used and that short firearms were seized. The child who died was a 2-year-old boy visiting his father, an inmate who was also hurt, El Financiero reported.
Relatives of inmates gathered outside the prison seeking information as security forces secured the perimeter.
Troops Move in to Restore Order
Members of the army, the National Guard and state security forces entered the prison following the clash to regain control of the grounds. Authorities said the penitentiary was “under control” afterward, and visits were suspended as a precaution. Visits resumed Saturday, Oct. 10, the state security secretariat said.
Sánchez Kondo said her office opened a homicide investigation that will also examine how weapons got into the prison and whether officials bear responsibility. No arrests had been reported as of Saturday, Oct. 10.
A Second Fight Leaves Two More Dead
Authorities found two more inmates dead during the morning roll call on Friday, Oct. 9, after what the state security secretariat described as a brawl inside one of the prison’s modules. Early reports pointed to stab wounds. Relatives blocked Mexico Highway 15 at Mazatlan’s southern exit that afternoon to demand information, Noroeste reported, and Sinaloa’s interim governor, Graciela Domínguez Nava, announced plans for a new federally funded penitentiary in Culiacan to ease crowding.
A Prison System Under Strain
Overcrowding has long been identified as a driver of bloodshed behind bars in Mexico. Analysts point to the heavy use of pretrial detention, which keeps thousands of prisoners locked up without a sentence, along with a shortage of prison staff, as conditions that have fed corruption and violence inside the country’s lockups.
Mexico’s prison population reached 261,388 people in February, according to official figures reported by Record, and about 148 prisons were over capacity.
El Castillo is not the first Sinaloa lockup to erupt. A May 31 riot at the Aguaruto prison in Culiacan, the state capital, left seven inmates dead and another injured.
Cartel Warfare Grips Sinaloa
The state has been a battleground for rival wings of the Sinaloa drug-trafficking cartel. Violence surged in September 2024 amid an internal power struggle between two factions, pitting the sons of convicted former drug lord Joaquín “El Chapo” Guzmán, known as “Los Chapitos,” against followers of Ismael “El Mayo” Zambada, another former cartel leader who has been detained.
The bloodshed has made Sinaloa one of the Mexican states that the U.S. State Department tells Americans not to visit because of security concerns. Mazatlan, a Pacific resort and shipping hub, sits at the southern end of a state where shootouts, roadblocks and disappearances have become routine features of daily life.
The riot also lands at a politically delicate moment. Mexico’s government is facing pressure from the Trump administration to intensify its campaign against the cartels, a demand that has put the security situation in states such as Sinaloa under intense scrutiny on both sides of the border.
What turned a routine visiting day into a massacre remains for prosecutors to determine.
