Federal authorities are investigating veteran State Department diplomat and longtime Pakistan expert Robin L. Raphel as part of a counterintelligence probe and have withdrawn her security clearances, U.S. officials say. The FBI searched Raphel’s Northwest Washington home last month and her State Department office also was examined and sealed, officials said. Raphel was placed on administrative leave last month and her contract with State was allowed to expire this week. Two U.S. officials described the probe as a counterintelligence matter, which typically involves allegations of spying on behalf of foreign governments. Raphel has not been charged with any offense. A spokesman for Raphel said she was cooperating with investigators but has not been told the “scope or nature or that she is the target” of any probe.