DALLAS (AP) — A Dallas man convicted of online activity linked to the Anonymous hacking network served five days in federal prison after he was removed from home confinement.

The U.S. Bureau of Prisons won't say why Barrett Brown was incarcerated Thursday at the federal prison in Seagoville, just outside Dallas. And Brown himself says he still hasn't been told the reason for his prison stay before his Monday return to home confinement, but he believes it was for refusing an order.

Brown was sentenced to five years in prison in January 2015 but placed on home confinement last November. He said a federal prison official told him he must have prior bureau approval before giving interviews but didn't show him the rule.

Brown is set for early release on May 25.