Mining of Data Prompted Fight Over U.S. Spying

WASHINGTON, July 28 - A 2004 dispute over the National Security Agency's secret surveillance program that led top Justice Department officials to threaten resignation involved computer searches through massive electronic databases, according to current and former officials briefed on the program.

It is not known precisely why searching the databases, or data mining, raised such a furious legal debate. But such databases contain records of the phone calls and e-mail messages of millions of Americans, and their examination by the government would raise privacy issues.