detainee 　(名) 抑留者

Many of the detainees were held for entering Japan illegally or for staying in Japan in violation of the immigration law. Among the 23 were people seeking refugee status in Japan.

"Anxieties about being detained for an indefinite period, fears about deportation and strong reactions to detention are likely leading them to hurt themselves," an official of the Social Action Center of the Catholic Archdiocese of Osaka said.
　　（The Japan Times online, Sunday, October 10, 2004　の‘Suicide bids rife among detainees’の記事より）

　ちなみに
refugee :（名） 亡命者
deportation : （名）国外退去
bid :（名）招致　招くこと
rife :（名）はびこっていること