The Justice Department has opened another investigation into leaks of classified information, this time to determine who divulged the existence of President George W. Bush's secret domestic spying program. The inquiry focuses on disclosures to The New York Times about warrantless surveillance conducted by the National Security Agency since the Sept. 11, 2001, terror attacks on the United States, officials said. The newspaper recently revealed the existence of the program in a front-page story that also acknowledged that the news had been withheld from publication for a year. The delay, the Times said, partly was at the request of the administration and partly because the newspaper wanted more time to confirm various aspects of the program. "The leaking of classified information is a serious issue. The fact is that al-Qaida's playbook is not printed on page one, and when America's is, it has serious ramifications," White House spokesman Trent Duffy told reporters in Crawford, Texas, where Bush was spending the holidays.