it happened to me on my first visit to the US.
i was held in a room with bangladesh and pakistani people. to think that i was there for a training and had complete documents.
after two hours, i was just released, without reason. proceeded with my training. bad thing there is that I missed my connecting flight.

depende ata sa entry point..... i entered sa minneapolis where they seldom process filipinos. sanay ata sila pag LA, Sanfo o NY ang entry point.