Washington, D.C. ? Sen. Robert Byrd of West Virginia was hospitalized Tuesday after complaining of back pain following a fall at his home, his spokesman said.

Byrd, 90, the Democratic chairman of the Senate Appropriations Committee and the longest-serving senator in history, was staying overnight at Walter Reed Army Medical Center for observation, said spokesman Jesse Jacobs. It was not immediately clear whether he had suffered broken bones.

Jacobs said Byrd fell at his Virginia home Monday night. He came to his office Tuesday and was on the Senate floor to vote for an Indian health bill. But after noticing he was wincing in pain, Byrd’s staff recommended that he see the Capitol physician, who “smartly for a 90-year-old man advised him to go to Walter Reed for observation.”