The U.S. Securities and Exchange Commission temporarily suspended trading in two securities linked to cryptocurrencies on Sunday, citing investor confusion regarding the assets.

The halted securities are Bitcoin Tracker One and Ether Tracker One, the regulator said in a statement.

The suspension started Sunday and will last through Sept. 20, according to the statement, which explains:

“For example, the broker-dealer application materials submitted to enable the offer and sale of these financial products in the United States, as well as certain trading websites, characterize them as ‘Exchange Traded Funds.’ Other public sources characterize the instruments as ‘Exchange Traded Notes.’

“By contrast, the issuer characterizes them in its offering materials as ‘non-equity linked certificates.’ CXBTF and CETHF are listed and trade on the NASDAQ/OMX in Stockholm and have recently been quoted on OTC Link (previously ‘Pink Sheets’) operated by OTC Markets Group, Inc.”

Brokers who allow customers to trade Bitcoin Tracker One and Ether Tracker One or offer quotes on the securities during the halt could be subject to enforcement actions, the SEC said.

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