Binance Holdings Ltd., the largest cryptocurrency exchange, is being investigated by the Commodity Futures Trading Commission over concerns that it allowed Americans to place wagers that violated U.S. rules, according to people familiar with the matter.

The CFTC is seeking to determine whether Binance, which isn’t registered with the agency, permitted U.S. residents to buy and sell derivatives that the regulator polices, said the people, who asked not to be identified because the probe is confidential. Binance, which has an office in Singapore but says it lacks a single corporate headquarters, hasn’t been accused of misconduct and the investigation may not lead to an enforcement action.

The scrutiny is the latest sign that market watchdogs may thwart the crypto industry’s ambitions of becoming more mainstream for U.S. investors. The CFTC considers virtual currencies like Bitcoin and Ether to be commodities and claims jurisdiction over their futures and other derivatives. That means crypto platforms face strict customer protection and oversight demands if Americans are trading on them -- regardless of where exchanges are based.

Binance said that it never comments on its communications with regulators, while adding that the company is committed to complying with rules. For instance, Binance blocks U.S. residents from its website and uses advanced technology to analyze deposits and withdrawals for signs of illicit transactions, the company said in a statement.

“We take a collaborative approach in working with regulators around the world and we take our compliance obligations very seriously,” Binance said. The CFTC declined to comment.

U.S. Crackdown

The investigation adds to the U.S.’s growing crackdown on crypto. The CFTC has already sued BitMEX for failing to register as a broker, with the exchange’s market share declining since it became a target of regulatory scrutiny. Coinbase Global Inc., the U.S.’s biggest crypto exchange, also disclosed last month that it’s responding to a wide-ranging CFTC probe.

Separately, the U.S. Treasury Department is considering new rules that would force banks to record the identities of those who invest in virtual assets. While advocates say the move would crack down on money laundering and other illegal activities, Bitcoin holders argue it would undermine a key draw of cryptocurrencies: the ability to send funds without government oversight.