A prisoner, Saifur Rehman serving a life sentence at the Haripur Central Prison died of cardiac arrest on Wednesday, reported a private media outlet.
Rehman, a native of Khyber Agency, was imprisoned in a narcotics case with a 25-year life sentence.
He had already spent 10 years in prison as part of his sentence.
Most prisons in Pakistan are packed more than their official capacity, which often leads to further criminalisation of prisoners, spread of diseases and poor living conditions.
