Federal authorities are investigating the loss of a computer hard drive containing a huge quantity of personal information from Bill Clinton’s presidency in an apparent security breach at a National Archives record center, government officials said Tuesday.

Government officials briefed on the matter said the breach, which was confirmed in April, involved the loss of a drive containing a terabyte of computerized data, which could include millions of individual pieces of information, including personal information about one of then Vice President Al Gore’s three daughters.

The missing information included Social Security numbers and home addresses of numerous people who visited or worked at the White House, along with other material related to security procedures used by the Secret Service at the White House in the Clinton years.