Federal agents were piecing together on Tuesday how a small bomb ended up in a mailbox outside a New York home owned by billionaire financier George Soros.
Soros, one of the world's biggest donors to liberal groups and causes, was not there at the time on Monday.
Investigators have not named any suspects or disclosed a possible motive, but Soros has become a hated figure among some right-wing activists in the United States and Eastern Europe, and the target of a hostile media campaign by the nationalist government in his native Hungary.