U.S. Supreme Court Justice Clarence Thomas missed oral arguments Monday without explanation.
The 75-year-old Thomas also did not participate remotely in the proceedings, as justices sometimes do when they're ill or can't otherwise attend in person, reported the Associated Press.
Chief Justice John Roberts announced the absence, saying that Thomas would still participate in that day's cases by using briefs and transcripts of the arguments, but did not say whether he was sick, as the court sometimes discloses.
Thomas missed several court sessions two years ago with an infection and later took part in those cases.
He is the oldest current Supreme Court justice and the longest-tenured, having joined the court in 1991.