Bodies were found strewn around the maximum-security wing, the kitchen, a prison yard and a conjugal visits area after the pre-dawn riot at the Las Cruces federal prison in Acapulco, said the security spokesman for the state of Guerrero.
“The incident was triggered by an ongoing feud between rival groups within the prison,” the spokesman, Roberto Alvarez, told a press conference.
It was the latest deadly riot in Mexico’s chronically overcrowded prisons, where corruption abounds, inmates often have de facto control, and contraband weapons and drugs are rife.
The Guerrero governor has ordered an investigation of all prison staff, Alvarez said. State police have temporarily taken control of the prison, backed by federal police and the army, which set up a security cordon outside.
Officials initially gave a death toll of five and indicated the riot was limited to the maximum-security wing. But the toll soared as police searched the rest of the prison.
Three more inmates were wounded in the violence, Alvarez said.
Guards said some of the victims had their throats slit, according to an internal state police report. It also said gunshots had been fired in the maximum-security wing, apparently by prisoners.
There was a heavy security presence outside the prison, with soldiers and riot police encircling the compound and two helicopters hovering overhead.
Dozens of anxious relatives had gathered, demanding news on their loved ones. Some shouted at police and tried to force their way through the wall of officers’ shields.
This was Mexico’s deadliest prison violence since 49 inmates were killed in February 2016 in a riot at the Topo Chico prison in Monterrey, in the northeast.
Mexico’s prisons are frequently hit by riots, killings and jailbreaks. This year has already seen shoot-outs, fires and the escape of 29 inmates in the northern state of Tamaulipas.
That is the same state where seven people were killed, including three police, when officers stormed the Ciudad Victoria prison in June to regain control from prisoners who had been stockpiling guns.
In March, the son of Juan Jose Esparragoza, a founder of the powerful Sinaloa drug cartel, escaped from prison in Sinaloa, the northwestern state that is the cartel’s home base.
And the cartel’s kingpin, Joaquin “El Chapo” Guzman, has made two spectacular prison escapes, one in 2001 and another in 2015. Recaptured in 2016, he was extradited last January to the United States, where he is being held in solitary confinement.
Experts say organised crime networks often operate from inside Mexican prisons with the complicity of corrupt officials.
After the Monterrey riot last year, authorities found dozens of knives, cocaine and flat-screen TVs inside, highlighting the control drug cartels had over the prison.
Acapulco, a resort town on Mexico’s Pacific coast, has been hit by grisly violence between rival drug cartels in recent years.
It is just one of the hotspots in Mexico’s war on drugs.
The country has seen a wave of bloodshed in the past decade that has left more than 200,000 people dead or missing as drug cartels wage war on each other and Mexican security forces.