London - A computer disk containing the personal data of around 5,000 prison workers in Britain has gone missing, in another case of several similar incidents that have embarrassed the British government, a British tabloid reported Sunday.

Information including the names, employee numbers and perhaps the addresses of prison guards and other personnel were contained on a portable hard-drive that went missing in July 2007, although the ministry of justice to whom the data belonged was not informed by the data firm EDS until recently, said the News of the World.

The News of the World claimed it received access to a letter from EDS to the British prison service confessing to the loss of the data.

According to a source quoted by the paper, senior (prison) staff have gone to great lengths to keep this quiet. There are criminals out there who would love to get their own back on guards and governors. This could give them all the details they need to take revenge."

Justice Secretary Jack Straw announced an immediate investigation.

I am extremely concerned about this missing data," Straw said, adding that he "ordered an urgent inquiry into the circumstances and the implications of the data loss and the level of risk involved. I have asked for a report as to why I was not informed as soon as my department became aware of this issue. My officials are also in touch with EDS."