Listed bitcoin miner Marathon Digital Holdings (MARA) announced in a filing that it has received a subpoena from the U.S. Securities and Exchange Commission (SEC), which is investigating potential violations of federal securities laws, including related party transactions. Marathon Digital's first-quarter results were better than analysts' expectations, with revenue increasing to $51.1 million from $28.4 million in the previous quarter, and 2,195 bitcoins were produced, a 74% increase from the same period last year. Shares of the company fell about 12% on Thursday, underperforming other bitcoin mining peers.