A brutal fight broke out in a prison in the Mexican Pacific resort of Acapulco on Thursday, leaving at least 28 inmates dead in one of the worst outbreaks of violence in the country's troubled penal system in recent years.
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.
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.
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 shootouts, 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 a 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.
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.