In a letter to Sergeant-At-Arms Wilson Livingood, House Republicans urged him to review CAIR’s alleged ties to Hamas and “determine if CAIR is a security threat.”

Four House Republicans formally requested an investigation into the Council on American Islamic Relations this week after charging that the nation’s largest Muslim advocacy group tried to “infiltrate” Capitol Hill with interns.

The lawmakers based most of their claims on an internal memo and the book “Muslim Mafia,” which describes CAIR’s purported strategy to influence members of Congress on the Judiciary, Intelligence and Homeland Security Committees. They raised concerns about CAIR in large part because the Justice Department named the group as an unindicted co-conspirator in a terrorism case.