Ohmynews has published letters written by an American of Jamaican descent who was arrested for teaching English illegally in Korea. Due to an internet controversy followed by a sensationalist tv program demonizing English teachers earlier this year, migrant workers are no longer the only foreigners being regularly targeted by immigration police in Korea. This article fills in the background, while this one touches on another aspect of the controversy.
The letters, written from the detention centre in Yeosu, can be found here and here. They provide an excellent look at, and criticism of, the system from the inside, and detail the challenges faced not only by the foreign workers from all over the world he is confined with, but also by the prison guards, who work in 24 hour shifts.