WASHINGTON ( CNN ) -- The National Archives -- a repository of important government documents , including the U.S. Constitution -- has lost a computer hard drive containing large volumes of Clinton administration records , including the names , phone numbers and Social Security numbers of White House staff members and visitors . The National Archives has lost a hard drive containing large volumes of Clinton administration records . Officials at the Archives say they do n't know how many confidential records are on the hard drive . But congressional aides briefed on the matter say it contains `` more than 100,000 '' Social Security numbers , including one belonging to a daughter of then-Vice President Al Gore . It also contains Secret Service and White House operating procedures , the staffers said they were told . The hard drive was last seen in the National Archive 's complex in College Park , Maryland , sometime between October of last year and the first week of February . It was discovered missing in late March , prompting a thorough search for the small , 2.5 pound device , the Archives said . When it could not be located , the inspector general 's office opened a criminal investigation . On Wednesday , the Archives announced a $ 50,000 reward for information leading to its return . The Archives said no national security information is on the hard drive , nor any original documents . But they said it does contain `` personally identifiable information , '' and they take the loss `` very seriously . '' U.S. Rep. Darrell Issa , R-California , whose staff was briefed on the matter , said the House will hold a hearing Thursday on the incident . `` If they [ the National Archives ' staff ] ca n't handle a hard drive that may be sensitive properly , we need to ask the question , will they handle the most secret materials properly ? '' Issa said . The Archives Wednesday gave the following account of the disappearance : . Last October , the hard drive was moved from a `` secure '' storage area to a workspace where it was being used for routine recopying to ensure preservation of the records . But work was halted last year because archivists `` wanted to investigate using automated tools to generate inspection reports . '' Staffers were moved to other projects until an automated tool was found in mid-March -- that 's when they found the hard drive was missing . The device is described as a two terabyte Western Digital MY BOOK external hard drive , measuring 6.5 x 2.1 x 5.4 inches . More than 110 4-millimeter tape cartridges were copied onto the hard drive . The records included records from the Clinton Administration Executive Office of the President . The archives said no original records have been lost , and the Archives has a backup hard drive that will enable them to determine what information is on the missing device . The inspector general said at least 100 people had access to the area where the hard drive was left unsecured , and that janitors , visitors and others also passed through the area . The Archives said it is reviewing the data on a copy of the missing hard drive and compiling a list of people whose personal information may be compromised . It will notify individuals of the potential breach and will provide them with a year of credit monitoring , the Archives said . `` Because of the extremely large volume of data on the drive , we do not know yet the number of individuals whose privacy has been affected , '' the Archives said Wednesday . `` As individuals are identified , they will be notified . '' The Archives also said it has taken steps to improve security , including both physical control of records and the treatment of personal information .
Officials say they do n't know how many confidential records are on the hard drive . Congressional aides say `` more than 100,000 '' Social Security numbers on drive . '" Comment: