The material was identified by personal attorneys for Mr. Biden on Nov. 2, just before the midterm elections, Richard Sauber, special counsel to the president confirmed. The documents were discovered when Mr. Biden’s personal attorneys “were packing files housed in a locked closet to prepare to vacate office space at the Penn Biden Center in Washington, D.C.,” Sauber said in a statement to CBS News. The documents were contained in a folder that was in a box with other unclassified papers, the sources said. The sources revealed neither what the documents contain nor their level of classification. A source familiar with the matter told CBS News the documents did not contain nuclear secrets.