The former English teacher and photographer was found dead in his cell at HMP Full Sutton, near Pocklington in East Yorkshire on Sunday, after reports suggest he was attacked with a makeshift weapon.
The 33-year-old was serving 22 life terms for horrific crimes against Malaysian children as young as six months.
Huckle, from Ashford in Kent was jailed back in June 2016 after admitting 71 charges of sex abuse against children under 12.
He was being held at Full Sutton, prison for men in categories A and B about 10 miles east of York.
It holds some of the most difficult and dangerous criminals in the country, with a capacity for almost 560 inmates.
Huckle, a Baptist churchgoer used his religion to prey on vulnerable children.
He was compiling a paedophile's manual at the time of his arrest by the National Crime Agency.
Five of the youngsters were living in a children's home and on one occasion he took a girl out to celebrate her fifth birthday and molested her at his house in Kuala Lumpur.
Huckle, who studied IT at university in Malaysia, was arrested by National Crime Agency officials as he arrived at Gatwick Airport en route to spend Christmas with his family in 2014.
Officers seized Huckle's encrypted laptop and managed to uncover more than 20,000 indecent pictures and videos although there were other files they were unable to crack.
Humberside Police confirmed an investigation into Huckle's death has been launched.
A force spokeswoman said: "An investigation has been launched following an incident at HMP Full Sutton on Sunday 13 October.
"We were called shortly after 12.30pm reporting that a man had died at the prison.
"Humberside Police are working closely with the Prison Service to investigate the death of an inmate and at this time we are treating the death as suspicious."