28 CFR §44.304

1. (a)The Special Counsel may, on the Special Counsel's own initiative, conduct investigations respecting unfair immigration-related employment practices when there is reason to believe that a person or other entity has engaged or is engaging in such practices, and shall notify a respondent by certified mail of the commencement of the investigation.
2. (b)The Special Counsel may file a complaint with OCAHO when there is reasonable cause to believe that an unfair immigration-related employment practice has occurred no more than 180 days prior to the date on which the Special Counsel opened an investigation of that practice.