CHILD killer Jon Venables was recalled to prison because of 'very serious allegations', Justice Secretary Jack Straw said today.

It comes as we revealed how the 27-year-old's terrible past was discovered by shocked pals and led to a confrontation at work.

A national newspaper also claimed today that Venables was returned to custody for committing a serious sexual offence, although that has not been confirmed.

Sources told us a fight broke out at Venables' workplace after friends carried out their own detective work into suspicions he was James Bulger's killer.

Checks into his date of birth appeared to corroborate their suspicions and led to increasing anger among his peers.

We understand Venables had created a Facebook profile, using the identity given to him by the Home Office after his controversial release and new anonymity in 2001, and exchanged messages with friends.

But one outraged person, fuelled by incontrovertible evidence that this was the two-year-old’s killer, decided to try to expose him online.

A message was posted on Venables’s own social networking page, under his new name, which read: "Don't you know who this is?"

That comment, along with Venables’s profile, was subsequently removed.

Following the posting, an altercation took place at work from which Venables is said to have been pulled away and led to a complaint being made.