Television images showed National Guard troops surrounding the penitentiary as inmates in bloody clothes were taken out of the building. Behind the barriers, relatives of the prisoners, most of them women, waited for news of their loved ones, many of them in tears.
Most of those injured at Uribana prison in Lara state suffered gunshot wounds, said the hospital official, Ruy Medina.
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He called the death toll "alarming," saying it was based solely on bodies brought to the hospital.
Medina said the inmates began arriving at the hospital shortly before midday, and that 14 of the injured had wounds severe enough to require surgery.
Iris Varela, the government minister responsible for Venezuela's jails and prisons, said the riot was set off after inmates rebelled when prison authorities launched a sweep of the facility in search of illicit weapons.
Varela had said earlier in the day that there was an "undetermined number" of casualties from the melee. Attempts by AFP to get an update from the ministry later in the day were unsuccessful.
Varela said the attempt to "completely disarm" the prisoners had been undertaken as a result of tips indicating that "internal prison gangs that fight for control of the penitentiary planned to settle scores with each other."
Opposition parties did not wait long to attack the government, accusing it of exercising lax control over the prison system.
"Who will they blame for this massacre this time around?" an opposition leader Henriques Capriles asked in his tweet. A former presidential candidate, Capriles lost last October's election to President Hugo Chavez.
"The government is incapable and irresponsible," he added.
Humberto Prado, head of the non-governmental Venezuelan Prison Monitoring Organization said that so far, the Venezuelan government "had failed to take responsibility for the events" and instead was "piling blame on the media."
The situation in Uribana prison had been monitored by the Inter-American Court of Human Rights since 2006, he added.
"The court told the Venezuelan government that no more inmates should be dying in this jail, but the government did not comply with this request, and now we have such a serious outburst of violence," he said.
Venezuela is infamous for the lamentable state of its prisons, especially for their overcrowding, which is among the worst in Latin America. Low sanitary standards and high levels of violence present additional challenges.
While the country's prisons have been built to house 14,000 inmates, there are almost 50,000 prisoners behind bars here.
As a consequence, violence is rampant.
Last August, at least 25 people were killed and 43 wounded during a clash between rival gangs in Yare I prison located outside of Caracas. And about 30 people were killed in a riot that erupted in Rodeo prison in June of 2011.
