<p>WASHINGTON — FBI agents arrested a Portland, Ore., man Thursday as part of the investigation into the deadly train bombings in Spain, federal officials said.</p>
<p>Brandon Bieri Mayfield, a U.S. citizen, was taken into custody on a material witness warrant, said a senior law enforcement official, speaking on condition of anonymity. The arrest, first reported in Newsweek, is the first known in the United States with connections to the March 11 bombings in Madrid.</p>