WASHINGTON, March 19 — Attorney General Alberto R. Gonzales was “extremely upset” that his deputy told Congress last month that a federal prosecutor had been fired for no reason, according to e-mail released Monday by the Justice Department.

Mr. Gonzales believed that the prosecutor, H. E. Cummins III, the United States attorney for Arkansas, was dismissed for performance reasons, the e-mail suggested. But his deputy, Paul J. McNulty, testified that Mr. Cummins had been replaced to create a vacancy for J. Timothy Griffin, a political ally of the White House political adviser Karl Rove.

The e-mail messages, among more than 3,000 released by the Justice Department, reflect the tensions at the highest levels of the agency as officials tried to contain the political brushfire set off by the dismissals of eight federal prosecutors last year.

Agency officials said the documents showed the dismissals had been over performance, not politics, as critics have charged.