Inmates rioting at a jail attacked other prisoners, killing eight, and took four police officers hostage Wednesday, authorities said.
State Police Chief Jesus Berro said a group of inmates obtained keys to several cell blocks and fatally shot eight fellow prisoners inside the jail in the city of San Cristobal, capital of Tachira state.
"We will begin an investigation to find out how firearms entered the jail," Berro said.
Contraband such as guns and drugs are commonplace in Venezuela's overcrowded prisons.
Berro told the state-run AVN news agency the rebellious inmates, who purportedly belong to a gang, resorted to violence as a way to protest long delays that have prevented their cases from being heard in court.
Many inmates have been held for months and even years while waiting for their cases to be heard. Prisoners air their grievances by regularly seizing relatives of inmates during visiting hours or taking guards as hostages.
Inmates at another prison took dozens of hostages last month, sparking a standoff that heightened tensions in the country's notoriously violent prison system.
Those hostages were released by inmates at the Tocuyito prison after authorities agreed to transfer 400 inmates to a jail closer to courts where their cases would be heard.
President Hugo Chavez has recognized prison crowding and rampant violence as a severe problem, and his newly appointed prisons minister, Iris Varela, has pledged to come up with solutions.
"We have to humanize the penitentiary system," Chavez said Wednesday on state television.
Chavez did not discuss the violence at the jail in San Cristobal.
"We are going to overcome all these problems that have come up," Varela said of widespread prison violence.
Venezuela's 30 prisons were designed to hold about 12,000 prisoners but are currently packed with about 47,000 inmates, according to official figures.