New Delhi, June 5 : A 23-year-old undertrial prisoner died after he consumed an unknown substance in Delhi's Mandoli jail, an official said on Monday. The deceased was identified as Mustkeem (23). According to police, on June 2, information was received at Harsh Vihar police station from GTB Hospital that Mustkeem, who was lodged in Central Jail No 13, Mandoli Jail, was brought to the hospital in an unconscious state after consuming an unknown substance and declared dead. "As death of the UTP was unnatural, duty Metropolitan Magistrate (MM) of Karkardooma Court was informed accordingly, and is conducting proceedings under Section 176 CrPC. On MM Dev Chaudhary's directions, the post mortem of the deceased was conducted on Monday by a medical board of three doctors at GTB Hospital's mortuary and the viscera was preserved," said a senior police official. "Opinion on cause of death is kept pending till the chemical analysis of viscera is received from FSL. Mustkeem was in Mandoli Jail for a case registered under section 380 (theft), 454 (house-breaking) and 411 (retaining any stolen property) of the Indian Penal Code at Gokulpuri police station," said the official. /IANS