Health bosses have apologised after a memory stick containing patient information was lost at Preston Prison.
An urgent investigation was launched after the USB data stick – with the password attached to it on a memo note – went missing on Tuesday, December 30.
The stick may have contained information of up to 6,360 patients. However, in some cases, individual patients had more than one entry.
All patients are, or have been, a prisoner at HMP Preston, on Ribbleton Lane.
Health bosses today admitted the memory stick was encrypted, but the password had been attached to the device when it went missing.
A thorough search has been undertaken by Primary Care Trust staff as well as HMP Preston's dedicated search team, but the data stick has still not been found.
Workers from NHS Central Lancashire involved in the incident have been suspended while the investigation takes place.
It is believed a member of NHS Central Lancashire staff had uploaded the information using the memory stick then returned to the administration office and lost the device somewhere on route.
Health chiefs have apologised for the breach and have taken urgent action to prevent it happening again.
Joe Rafferty, chief executive of NHS Central Lancashire, said: "We are deeply sorry – this should never have happened.
"We have launched a full and thorough investigation and we are taking all necessary steps to ensure it cannot happen again.
"Even though there is no risk to anyone's ongoing treatment or care, we have plans in place to contact those affected to inform them of the breach and apologise."
A Prison Service spokesman said: "We are aware of this incident and are working closely with Central Lancashire PCT to manage any risks. There is no risk to prison security."
The information included prisoners' surnames, prison number, cell location, age range, prison clinic appointment times and references to medical conditions such as asthma, diabetes, mental health and even sexual health references.
The USB data stick did not contain any other information such as first names, dates of birth, NHS numbers or home contact details or any financial information.
Anyone with concerns should contact the PCT's confidential information line on: 0845 609 9866. It is open 9am to 5pm seven day's a week until January 23, 2009.
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