A prisoner died of cardiac arrest  yesterday morning. He suffered the attack at the district jail.  The deceased has been identified as Mujibur Rahman, 38, an inhabitant of Jartrabari area in Dhaka. Mujibur was held on August 24 when he was carrying drugs in a microbus.  Ashum Kumar Saha, RMO of Feni Sadar Hospital, said Mujibur was admitted at the hospital yesterday morning after he complained of chest pain.