WASHINGTON — A group of powerful bank regulators on 3 January highlighted what they said were a litany of risks stemming from cryptocurrencies and expressed scepticism that the assets can be safely held by the financial institutions they oversee.

The Federal Reserve, Federal Deposit Insurance and Office of the Comptroller of the Currency said that recent failures of major crypto firms led them to exercise caution in reviewing banks’ proposals to engage with the market. They highlighted fraud and scams, market volatility, legal uncertainty, and weak risk-management and governance practices at crypto firms, among other things, as reasons for concern.