U.S. law enforcement agencies thwarted an attempt to blow up a car bomb at an annual Christmas tree lighting ceremony in Portland, Oregon, and arrested the suspected bomber, officials said early Saturday. The Justice Department identified the chief suspect as 19-year-old Mohamed Osman Mohamud of the town of Corvallis, a naturalized US citizen of Somali descent. Mohamud was arrested by the Federal Bureau of Investigation and Portland police around 5:40 pm Friday (0040 GMT Saturday) after he attempted to remotely detonate what he believed to be an explosives-laden van that was parked near the tree lighting ceremony in Portlands Pioneer Courthouse Square, officials said. But the device was in fact a fake supplied by the FBI, and the public was never in any danger, they added.