He said an electrical short circuit may have sparked the fire.
Like most correctional facilities in Indonesia, the Tangerang prison is chronically overcrowded.
It holds more than 2,000 inmates, even though it was designed for a total of 600, according to the Justice Ministry.
Critics say overcrowding at Indonesian prisons has been caused by Indonesia’s aggressive war on drugs.
Most of the more than 28,000 drug convicts across Indonesian prisons are drug users who should not have been imprisoned in the first place, the Institute of Criminal Justice Reform, a non-governmental organization, said on Wednesday.