The fire at the Tocuyito facility in Carabobo state overnight left nine men and eight women dead, the prosecutor's office said.
No cause of the fire was given pending a probe led by three investigators.
The injured were being treated at a hospital in Valencia, the state capital.
A National Penitentiaries Ministry source told AFP the blaze was located in unit 1J, and apparently caused by a short circuit.
Venezuela's crowded prisons are among Latin America's deadliest. Government plans to improve conditions have not been met, rights groups say.
The Venezuelan Prisons Monitor, a non-governmental group, says that in 2014, 309 inmates -- many never convicted of anything -- were killed. Another 179 were injured in prisons that it says are at 170 per cent capacity.
