Jon Venables is understood to have been freed from prison after being locked up in 2010.
Venables has been granted parole again. Last time, he was sent back to jail for distributing indecent images of children.
This is how events unfolded from the abduction of James Bulger to the conviction of his schoolboy killers, Jon Venables and Robert Thompson.
One of James Bulger's killers was reportedly given a fourth new identity when he was released from jail again, the Daily Mail reported.
Jon Venables, 31, is understood to have been freed from prison after being locked up in 2010 for downloading images of child abuse.
– Ministry of Justice spokeswoman
We do not comment on individual offenders. The re-release of life licensed offenders is directed by the independent Parole Board once they are satisfied they can be safely managed in the community.
Their life licence lasts for the rest of their lives, and they may be recalled to prison at any time for breaching their licence conditions.
Additionally, they will be subject to strict controls and restrictions for as long as their risk requires them.
Denise Fergus, mother of James Bulger, told The Sun that her son's killer Jon Venables "lies for his own sick ends".
She said: "I have been told that the terms of his parole mean that he must not enter the county of Merseyside.
"But the Probation Service didn't monitor him properly last time so I have no faith in their ability to do that now.
"They should've kept him locked up for a long time."
James Bulger's father, Ralph, believes Jon Venables will commit more crime, a friend said.
The friend said: "He hasn't put a time on it but he is convinced he will reoffend."
She added that James's family were given scant information about Venables' release and Mr Bulger was told via his lawyer.
She said: "As ever they are kept in the dark. "They don't explain the terms of his release, I don't know whether they are going to."
One of James Bulger's killers is reported to have been released from jail for a second time.
Jon Venables, 31, was freed from prison after being locked up in 2010 for downloading images of child abuse, The Sun said.
Venables had previously served eight years for murdering two-year-old James in Liverpool in 1993.
The toddler's mother, Denise Fergus, told the newspaper Venables is "a danger to the public".
This has been updated to say that Jon Venables has been released from prison twice, not four times.
The mother of murdered toddler James Bulger said she feels like she has let her son down after learning one of his killers will be released.
In an interview with Channel 5 News, Denise Fergus said: "I just can't believe how I'm getting treated and I don't know why they're treating me like this."
The father of James Bulger says the decision to release one of his son's killers from prison "filled him with terror". Speaking through his solicitor, Robin Makin, he added:
"Ralph fears that an innocent person may be mistaken for Jon Venables and be injured or even killed. If such occurs then Ralph will feel guilty of not having done enough to have prevented such an obvious tragedy."