Bitcoin continued to be hugely volatile on Monday, losing a fifth of its value, dropping down to $30,500.
The cryptocurrency last week smashed record after record, eventually surging past $40,000.
In mid-afternoon European trade, Bitcoin was quoted at above $33,300.
Britain’s financial watchdog on Monday urged caution, especially among smaller investors.
The Financial Conduct Authority “is aware that some firms are offering investments in cryptoassets, or lending or investments linked to cryptoassets, that promise high returns”, it said in a statement.
“Investing in cryptoassets, or investments and lending linked to them, generally involves taking very high risks with investors’ money.
“If consumers invest in these types of product, they should be prepared to lose all their money,” the FCA added.