That process is accomplished by sending immigration detainers (Form I-247) to the prison or jail that is incarcerating the alien. Detainers — Notify the prison or jail that incarcerated aliens are subject to deportation charges or a deportation order and that ICE intends to put them in removal proceedings or execute their deportation orders when they finish their sentences; Ask the prison or jail to notify ICE when such aliens are about to be released; and Ask them to retain custody for up to 48 hours beyond the time when they otherwise would be released to provide ICE with time to pick them up.