Bureau of Corrections spokesman Roberto Olaguer says Thursday's blaze was the second in two years to hit the Leyte Regional Prison in Leyte province in the center of the country.
Olaguer says the fire may have been caused by faulty wiring in the building that was built after the earlier fire in 2013.
Philippine prisons are notoriously overcrowded and have poor facilities. The Leyte prison houses more than double its capacity of 500 stated on the Bureau of Corrections website, which also said that its facilities are "often below par" compared to other prisons.
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