A Prison Service spokeswoman said: "An incident at HMP Long Lartin on Thursday February 14 resulted in the death of prisoner Subhan Anwar.
"Two prisoners are now in police custody and the matter is being investigated by police."
Two prisoners are being held in police custody after Subhan Anwar, who was jailed for torturing and murdering his partner's two year old daughter, was found dead in his cell, the Ministry of Justice said.
Anwar, who was jailed for a minimum of 23 years in 2009 for the murder of Sanam Navsarka, is understood to have been held hostage in a cell at HMP Long Lartin in Worcestershire before he was killed.
His partner, Zahbeena Navsarka, was cleared of her daughter's murder but found guilty of manslaughter and jailed for nine years.