The United States Commodity Futures Trading Commission, or CFTC, has added 34 unregistered foreign entities to its Registration Deficient List, including at least six providing crypto-related services.

In a Thursday announcement, the CFTC said it had expanded its list of firms that it requires to register with the CFTC for providing services including trading binary options, foreign currency or other products such as cryptocurrencies. The additions to the Registration Deficient List, or RED list, include B.O TradeFinancials, CryptoBO, Bitpay Options, CryptoSphereFX, Direct Cryptos and Prime Crypto FX.

Since 2015, the CFTC has placed 202 companies on the RED List, warning U.S.-based investors to be cautious “when participating in products or markets that historically have seen a large number of fraud complaints.” Some of the websites linked to the crypto firms added on Thursday were not live at the time of publication.

“Because they are not registered with the CFTC, customers engaged in transactions with these entities may not receive the benefit of the customer protections, safeguards and guardrails long-adopted and deeply embedded in the CFTC’s oversight of the markets,” said CFTC commissioner Kristin Johnson. “Transacting with unregistered entities, particularly those operating without such oversight and beyond our borders, may expose U.S. customers to significant and concerning risks.”

Related: CFTC brings $1.7B fraud case involving Bitcoin against South African national

Along with the Securities and Exchange Commission, the CFTC is one of the few U.S. government departments with the authority to bring enforcement actions in cases involving crypto firms. However, due to the lack of a clear framework for digital assets, many industry experts have voiced concerns about the patchwork nature of regulations needed to operate in the United States. In June, lawmakers introduced a bill aimed at addressing how the SEC and CFTC could handle different responsibilities in the digital asset space.