A military operation to disarm prison inmates erupted into a riot that left at least 54 dead and 88 injured in western Venezuela, dpa quoted the Venezuelan daily El Universal as reporting. "There was a situation of tragic confusion that we really regret," Venezuelan Vice President Nicolas Maduro said Saturday. Maduro said an investigation has been launched onto events Friday at Uribana prison. Prison Services Minister Iris Varela said it was necessary to use the National Guard to conduct the search operation after receiving information that rival inmate gangs were armed.