28 C.F.R. § 8.5 – Custody.

(a) All property seized for forfeiture by ATF, DEA, or FBI shall be delivered to the custody of the U.S. Marshals Service (USMS), or a custodian approved by the USMS, as soon as practicable after seizure, unless it is retained as evidence by the seizing agency.
(b) Seized U.S. currency (and, to the extent practicable, seized foreign currency and negotiable instruments) must be deposited promptly in the Seized Asset Deposit Fund pending forfeiture. Provisional exceptions to this requirement may be granted as follows:
1. (1) If the seized currency has a value less than $5,000 and a supervisory official within a U.S. Attorney's Office determines in writing that the currency is reasonably likely to serve a significant, independent, tangible evidentiary purpose, or that retention is necessary while the potential evidentiary significance of the currency is being determined by scientific testing or otherwise; or
2. (2) If the seized currency has a value greater than $5,000 and the Chief of the Asset Forfeiture and Money Laundering Section (AFMLS), Criminal Division, determines in writing that the currency is reasonably likely to serve a significant, independent, tangible evidentiary purpose, or that retention is necessary while the potential evidentiary significance of the currency is being determined by scientific testing or otherwise.
(c) Seized currency has a significant independent, tangible evidentiary purpose as those terms are used in § 8.5(b)(1) and (b)(2) if, for example, it bears fingerprint evidence, is packaged in an incriminating fashion, or contains a traceable amount of narcotic residue or some other substance of evidentiary significance. If only a portion of the seized currency has evidentiary value, only that portion should be retained; the balance should be deposited.