Japan Exchange Group is considering measures to limit the growth of listed digital-asset treasury companies, as concerns deepen over losses connected to the crypto hoarding frenzy.

The Tokyo Stock Exchange operator is exploring options including a stricter application of its backdoor listing rules and requiring firms to undergo a fresh audit, according to people familiar with the matter, who asked not to be named as the plans are private. No official course of action has been determined at this point, they added.

Since September, three listed Japanese companies have put plans to start buying cryptocurrencies on hold due to pushback from JPX, according to one of the people. Those companies have been told their fundraising abilities will be restricted if they pursue buying crypto as a business strategy, the person said.