At least 31 inmates have died in a prison in southern Ecuador, including 27 who were hanged, following clashes between rival gangs at El Oro prison in Machala.

Four prisoners were killed and over 30 injured in the initial violence, which erupted amid plans to transfer inmates to a new facility.

Ecuador’s overcrowded prisons have repeatedly seen deadly gang violence, with hundreds killed in recent years.

Authorities are building a new maximum-security prison, El Encuentro, set to open in late November, aimed at improving security and separating rival gangs, the BBC has reported.

Prison gangs like Los Lobos and Los Choneros, which have been linked to violent crime, were recently designated as Foreign Terrorist Organizations by the U.S. Department of State.