Why were japenese americans placed in POW camps?

Some Japanese Americans were in POW camps in Japan; some were in internment and detention camps in the US; most were in relocation centers in the US; and many thousands were never in any camp or center in the US at all during WWII. But the big surprise is that many thousands of Japanese Americans spent the entire war in Japan in no camp at all, with some, in fact, serving even in the Imperial Japanese Armed Forces. You'll have to do your own research to find out why all this was so. See the source here for many answers.