Upvote:3
Since this was front page news in local newspapers (cf. San Francisco Examiner, February 1942), this was known and observed by the public:
American public opinion initially stood by the large population of Japanese Americans living on the West Coast, with the Los Angeles Times characterizing them as "good Americans, born and educated as such." Many Americans believed that their loyalty to the United States was unquestionable.
But, six weeks after the attack, public opinion along the Pacific began to turn against Japanese Americans living on the West Coast, as the press and other Americans became nervous about the potential for fifth column activity. Though the administration (including the President Franklin D. Roosevelt and FBI Director J. Edgar Hoover) dismissed all rumors of Japanese-American espionage on behalf of the Japanese War effort, pressure mounted upon the Administration as the tide of public opinion turned against Japanese Americans. Civilian and military officials had serious concerns about the loyalty of the ethnic Japanese after the Niihau Incident which immediately followed the attack on Pearl Harbor, when a civilian Japanese national and two Hawaiian-born ethnic Japanese on the island of Ni'ihau violently freed a downed and captured Japanese naval airman, attacking their fellow Ni'ihau islanders in the process.
See the references in the cited wikipedia page.