The Attorney General has launched an investigation after photographs purporting to show killer Jon Venables were allegedly posted on the internet.
Venables was 10 when he and classmate Robert Thompson abducted and murdered two-year-old James Bulger in Liverpool in February 1993.
Thompson and Venables were jailed for life but released on licence with new identities in 2001.
The murder of James Bulger still provokes strong reactions nearly 20 years later
Dame Elizabeth Butler-Sloss, of the High Court Family Division, made an unprecedented court order banning publication of any information which could lead to the revelation of their new identities.
Venables, now 30, had his parole revoked in 2010 and was jailed for two years after admitting downloading and distributing indecent images of children.
The images, which appeared on the social network site Twitter, claimed to show an adult Venables posing with friends. The Twitter user has since removed the posts.
A spokesman for the Attorney General's office said: "The AGO has been alerted to a possible contempt of court. We are liaising with the MoJ (Ministry of Justice) and others to establish the facts.
"We can neither confirm nor deny whether the pictures in question are of Jon Venables. It should be noted, there is a worldwide injunction in place which prevents the publication of any images or information purporting to identify anyone as Jon Venables."
James Bulger's mother, Denise Fergus, has made no comment about the alleged breach.
Fergus, 45, has always opposed the injunction, fearing it could lead to innocent men being accused of being James's killers.
Venables and Thompson abducted James from the Bootle Strand shopping centre in Merseyside before torturing and killing him.
The two boys, who were truanting from school, walked James around the streets of Liverpool for more than two miles, stopping occasionally to kick and punch him.
They told adults who intervened that he was their brother.
After taking him to a nearby railway line, they left his body on the tracks in the hope it would be destroyed by a train.
The toddler had been splattered with blue paint and his battered head lay surrounded by a pile of bricks.
His body was found two days later by children playing on a freight railway line.