49 CFR 190.293: Criminal referrals.

(a) If a PHMSA employee becomes aware of any actual or possible activity subject to criminal penalties under § 190.291, the employee must report it to the Office of Chief Counsel, Pipeline and Hazardous Materials Safety Administration, and to the employee's supervisor. The Chief Counsel may refer the report to the Associate Administrator to investigate. If appropriate, the Chief Counsel shall refer the report to the Office of Inspector General, or other law enforcement as appropriate (with notification to the Office of Inspector General as soon as possible).

(b) A PHMSA employee also has the option of making a direct referral to the Office of Inspector General (OIG), either by directly contacting an OIG investigator, or via the OIG hotline at 800-424-9071, at https://www.oig.dot.gov/hotline, by email at hotline@oig.dot.gov, or by mail to the Office of Inspector General, 1200 New Jersey Ave. SE, West Bldg. 7th Floor, Washington, DC 20590.