So we learn from this Associated Press story. It hints that the records' acquisition may stem from a DOJ inquiry into the disclosure, last year, of classified material to the AP---regarding the CIA's disruption of an AQAP effort to blow up a bomb on an airplane traveling to the United States. (The AP broke the AQAP bomb story in May.)
From today's article:
WASHINGTON (AP) — The Justice Department secretly obtained two months of telephone records of reporters and editors for The Associated Press in what the news cooperative's top executive called a "massive and unprecedented intrusion" into how news organizations gather the news.
The records obtained by the Justice Department listed outgoing calls for the work and personal phone numbers of individual reporters, for general AP office numbers in New York, Washington and Hartford, Conn., and for the main number for the AP in the House of Representatives press gallery, according to attorneys for the AP. It was not clear if the records also included incoming calls or the duration of the calls.
In all, the government seized the records for more than 20 separate telephone lines assigned to AP and its journalists in April and May of 2012. The exact number of journalists who used the phone lines during that period is unknown, but more than 100 journalists work in the offices where phone records were targeted, on a wide array of stories about government and other matters.