Nineteen prisoners were killed and a dozen wounded in the second riot in less than a week at a jail in the Mexican border city of Tijuana, local officials said on Thursday.
"Up to the last count, there are 19 dead and 12 wounded," Daniel de la Rosa, Baja California's state police chief, said in a televised news conference following the riot on Wednesday at one of Tijuana's main jails.
Authorities have regained control of the prison and transferred 200 dangerous inmates to other facilities, Baja California Gov. Jose Osuna said at the news conference.
On Sunday, four prisoners were killed and a large part of the same jail destroyed in a clash between guards and inmates.
Family members of inmates housed in the overcrowded jail had complained of prisoner abuse and local media said the death of an inmate could have sparked the violence.
Tijuana, just south of San Diego, is a major corridor for drug trafficking and has seen violence soar in recent months even as President Felipe Calderon deployed thousands of troops to the city and across the country to crack down on warring cartels. More than 2,700 people have been killed in drug violence this year in Mexico.
'The guards are assassins'
On Wednesday evening, inmates hung messages and shouted slogans from the prison's roof and windows. Some also waved Mexican flags.
Several messages claimed that prison guards had killed at least two prisoners, beating one man to death on Saturday and killing the other last week.
"No more dead," one banner read. "The guards are assassins."
The rioting prisoners said they want longer visiting hours and the ability to see people who aren't direct family.
Soldiers and police surrounded the building, and a helicopter clattered overhead. Family members trying to find out information on those inside gathered at police cordons and clashed at least twice with security officials.
The riot began during visiting hours, and prisoners said several visitors were in the prison compound but were not being held hostage and had been fed.