Berkshire Hathaway Inc, run by billionaire Warren Buffett, on Friday warned investors it has no affiliation with a purported cryptocurrency brokerage website using the Berkshire Hathaway name.

The website describes its operator as a Texas-based broker founded in 2020 to give investors “an opportunity to achieve a completely passive income from investment in cryptocurrency mining.”

It includes purported customer testimonials and says the broker is regulated in the United States, United Kingdom, Cyprus and South Africa, using incorrect names for two regulators. Its email format differs from that of Buffett’s company.

Buffett has long been skeptical of cryptocurrency, and in 2018 called bitcoin “rat poison squared.” In a statement, Buffett’s company said it learned about the website, berkshirehathawaytx.com, on Friday afternoon.

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“The entity who has this web address has no affiliation with Berkshire Hathaway Inc or its Chairman and CEO, Warren E. Buffett,” Berkshire said. The website’s operator did not immediately respond to requests for comment.

Buffett has run Berkshire Hathaway Inc since 1965. The Omaha, Nebraska-based conglomerate owns several dozen companies including the BNSF railroad and Geico auto insurer, and as of Sept. 30 owned more than $306 billion in stocks.

Cryptocurrency has come under renewed scrutiny recently. This week, U.S. crypto investors sued FTX founder Sam Bankman-Fried and several celebrities who promoted his exchange including NFL quarterback Tom Brady and comedian Larry David, claiming they engaged in deceptive practices to sell FTX yield-bearing digital currency accounts. FTX filed for bankruptcy and is facing scrutiny from U.S. authorities amid reports that $10 billion in customer assets were shifted from FTX to Bankman-Fried’s trading company Alameda Research.