ATLANTA -- U.S. Rep. John Lewis was released from a hospital Sunday evening, having been given a "clean bill of health," according to a spokesperson.

Lewis, 78, was hospitalized Saturday night for undisclosed reasons.

His spokesperson said all tests have been completed, and that Lewis "thanks everyone who shared their thoughts, prayers and concerns during his stay. "

Lewis, a Democrat, played a key role in the civil rights movement and marched with the Rev. Martin Luther King Jr. in 1965 in Selma, Ala.

Lewis was expected at an Atlanta event Saturday evening but did not attend.