Delhi gang-rape main accused Ram Singh committed suicide on Monday around 5 a.m. by hanging himself inside jail number 3 of Tihar Jail.
A magisterial inquiry has been ordered in the case, as Union Home Ministry has sought report from the jail authorities on Ram Singh's suicide.
The Union Home Ministry Monday sought a detailed report from the Tihar Jail administration hours after Singh committed suicide in his cell.
Minister of State for Home RPN Singh said: "The Home Ministry has demanded a detailed report from the Delhi Police and the Tihar jail administration into the suicide of Ram Singh."
The incident came to light around in the morning, as Ram Singh was rushed to the jail hospital, but was declared dead on arrival.
The body was then sent for postmortem at Deen Dayal Upadhyay (DDU) hospital. A forensic team has reached the jail to get evidence in this case.
Tihar jail sources said Ram Singh, the prime accused in the December 16, 2012, Delhi gang rape murder case, hung himself using his clothes probably his own shirt. The incident came to fore when the guard spotted him this morning.
Ram Singh was to be produced in Saket court along with other accused in the case today.
Singh was the driver of the bus in which the 23-year-old physiotherapist student was gang-raped by him and his five associates, including a minor, in south Delhi after brutally beating her and her male friend.
Ram Singh, along with the other four accused, was charged with murder, gang-rape, destruction of evidence, criminal conspiracy, dacoity, unnatural sex and common intent in the case. The sixth accused is a Juvenile and is in an observation home.
Ram Singh's death has posed serious questions on the security provided to the accused as all of them were under 'suicide watch after they had stopped talking and interacting amongst themselves.
The Tihar Central Jail complex has several jails, each identified by a number. While Pawan, 19, and Akshay, 29, are held in Jail No 4, Vinay, 20, and Mukesh, 26, are in Jail No 7.
The Tihar Jail authorities have ordered an inquiry into the incident and a post-mortem will be conducted on Singh's body soon.
Singh was arrested soon after the December 16 incident from near his home in R K Puram.
The girl died in a Singapore hospital on December 29. (ANI)