Clinton Is Recovering From a Concussion

As a result, she will not testify as scheduled on Thursday before Congressional committees investigating the September attack on the American diplomatic outpost in Benghazi, Libya. The fainting episode occurred after Mrs. Clinton, who is being widely discussed as a possible presidential candidate in 2016, became dehydrated because of a stomach virus she contracted during a trip to Europe, according to statements released by a close adviser and her doctors.

One State Department official said Mrs. Clinton fainted when she was alone at her home in Washington but added that the concussion was not diagnosed until Thursday. He said the concussion was not severe.

William J. Burns and Thomas R. Nides, both deputy secretaries of state, will testify to the Senate Foreign Relations Committee and the House Foreign Affairs Committee in Mrs. Clinton’s place, according to the panels.

Besides the Congressional hearings, the State Department is preparing for an eventful week on the Benghazi attack, which had led to partisan fighting about what precipitated the attack and what arrangements were made to defend the compound.

On Monday, an independent panel that was established to investigate the attack is expected to present its report to the State Department. The panel, called an accountability review board, is led by Thomas R. Pickering, a veteran diplomat. It includes four other members, including Mike Mullen, the retired admiral who served as chairman of the Joint Chiefs of Staff. The board is authorized by a 1986 law intended to strengthen security at United States diplomatic missions.