Williams died of a cardiac arrest after being beaten
Australian officials are investigating how a notorious gangland murderer came to be killed in a high security prison.
Carl Williams, 39, died on Monday of a cardiac arrest, after being beaten with part of an exercise bike.
A 36-year-old fellow inmate, who has not been named, has been charged with murdering Williams.
Police officials have said they are concerned Williams' death could trigger a new "spiral of violence" between Melbourne's criminal gangs.
"We're obviously looking at the implications of yesterday's events to try and understand where this might go and do everything we can to make sure that we don't go back into a spiral of violence," Victoria Police Chief Commissioner Simon Overland said.
"We need to do everything we can to make sure that we manage the consequences of Carl Williams' murder."
Victoria Premier John Brumby said there would be "a number of investigations" into the death.
"One obviously by the coroner, but of course another by Victoria Police and prison authorities," ABC news quoted him as saying.
Mr Brumby said he was "obviously concerned" by the murder, which had raised serious questions about the safety of inmates in high security prisons.
Victoria's Deputy Police Commissioner Sir Ken Jones has been appointed to lead the investigation, but there have also been calls for an independent anti-corruption inquiry.
Williams' lawyer, Rob Stary, said a murder inquiry would "only deal with the immediate circumstances surrounding Mr Williams' death. It won't look at the broader issues."
"Certainly there are no cohesive powers in any of those investigations that would compel people to answer questions and it will look at the individual circumstances surrounding this death," ABC quoted Mr Stary as saying.
Williams, commonly known as Fat Boy, had been a central figure in Melbourne's gangland wars, in which 35 people were killed over a 20-year period.
He was jailed for a minimum of 35 years in 2007 for the murder of three gangland rivals.