Aliens who are in the United States illegally can expect detention or removal by Federal law enforcement. The United States Immigration and Customs Enforcement, or ICE, makes it a point to detain and remove any alien who they feel may have been admitted to this country via an oversight of some sort. Any alien who may pose either a national security or a public safety threat to others who are living in the United States will be dealt with in short order, provided the alien can be located. However, there are so many aliens at large that the ICE Office of Detention and Removal often is not able to ensure that all aliens will leave the country. 36% of all aliens in custody for the past three years were released due to needs for personnel, sleeping space, and funding problems.