NEW YORK, Oct 28 (Reuters) - U.S. Treasury debt yields turned lower in early afternoon trading on Friday after the head of the Federal Bureau of Investigation said the agency would investigate additional emails that have surfaced relating to Hillary Clinton’s use of a personal email server.

Clinton is the Democratic Party’s presidential nominee for the upcoming U.S. election.

FBI Director James Comey said in a letter to key Republican committee chairmen in the House of Representatives that it was unclear how significant the new materials may be.

Benchmark 10-year Treasury notes were up 2/32 in price to yield 1.837 percent, down from 1.843 percent late on Thursday.

U.S. 30-year bonds were flat in price to yield 2.601 percent, slightly down from Thursday’s 2.602 percent.

U.S. two-year note yields were at 0.860 percent, down from Thursday’s 0.884 percent. (Reporting by Gertrude Chavez-Dreyfuss; Editing by Bernadette Baum)