Biden says he was 'surprised' classified documents were found in his private office

US President Joe Biden said Tuesday that he was surprised to learn that classified documents from his time as vice president were found at the Washington, D.C. office of his think tank.

"People know I take classified documents, classified information, seriously," Biden told a news conference at the North American Leaders' Summit in Mexico City.

He said his lawyers were clearing out his office and found some documents in a box in a locked cabinet and realized there were several classified documents in the box.