Former Lostprophets frontman Ian Watkins, 48, was serving a 29-year sentence for child sex offences at HMP Wakefield.
Emergency services were sent to the prison, but Watkins was pronounced dead at the scene after an alleged attack on the morning of October 11.
Initially Rashid Gedel, 25, formerly of Fenman Gardens in Ilford, was charged with murder.
Another man, Samuel Dodsworth, 43, was also charged with murder.
West Yorkshire Police has announced today (October 21) that two further men, 23 and 39, have been arrested from HMP Wakefield on suspicion of conspiracy to murder.
They are both in police custody and will be interviewed over the course of today, they will then be bailed and returned to prison while enquiries continue.
Meanwhile Gedel and Dodsworth are on remand awaiting trial.
Ian Watkins’ list of offences
Watkins, 48, was jailed for 29 years in December 2013 with a further six years on licence, after admitting a string of sex offences – including the attempted rape of a fan’s baby.
The disgraced singer was arrested following the execution of a drugs warrant at his Pontypridd home on September 21 2012 when a large number of computers, mobile phones and storage devices were seized.
Analysis of the equipment uncovered Watkins’ depraved behaviour.
Among the disturbing videos due to be shown at his trial were his attempted rape of a baby and a webcam chat in which he instructed a crazed fan to abuse her child.
Watkins was given 14- and 15-year consecutive prison terms for engaging in sexual activity with a child and the attempted rape of an 11-month-old baby.
He was also convicted of 11 other offences – with those sentences running alongside his 29-year term.
Watkins was previously taken to hospital after being attacked in 2023.
