At least 21 inmates have been killed in a riot at a maximum-security prison in El Salvador.
Hundreds of police, soldiers and security guards were deployed
Security forces have now regained control of the Apanteos jail, near Santa Ana, 66km (41 miles) west of the capital, San Salvador.
The riot broke out on Friday when a member of the infamous Mara 18 gang began fighting a guard, sparking battles between hundreds of inmates.
The jail holds 2,000 inmates, some of them the most dangerous in the country.
Security sources described the scene in the jail as "horrible, a massacre", human rights prosecutor Beatrice Alamanni told AFP news agency.
"You can see feet and heads under rubble inside the cells," she said.
After the argument between the gang member and the guard, rival gang members began fighting among themselves with makeshift weapons such as shovels and pieces of broken masonry.
Hundreds of police, soldiers and security guards were deployed to restore order and some inmates have been transferred to other jails.
Prisons in Central America are often overcrowded - Apanteos was built to hold 1,800.