STORY: More trouble for Elon Musk, after the U.S. Securities and Exchange Commission hit the Tesla CEO with another subpoena over the billionaire's tweets.

Tesla disclosed on Monday that it had received a new subpoena related to "compliance with the SEC settlement" that required the Musk's tweets to be vetted by Tesla's lawyer's if they contained material information.

That agreement followed SEC scrutiny over Musk's 2018 tweet that he had "funding secured" to take Tesla private.

Since then, the SEC subpoenaed the electric car maker over a tweet from Musk that asked his Twitter followers whether he should sell 10% of his Tesla stake to cover tax bills on stock options.

Tesla said on Monday it will cooperate with the government authorities on the latest subpoena. The SEC declined to comment.

The regulator is also looking into Musk's tweets about his $44 billion deal to buy Twitter, asking him last month about a post in which he said the "deal cannot move forward" unless Twitter provided more data about fake accounts.

The trial over Twitter's lawsuit against Musk over abandoning the takeover is set to begin in October.

As if Musk's dance card wasn't full enough, the Wall Street Journal reported late on Sunday that Musk had engaged in a brief affair with Nicole Shanahan, the wife of Google co-founder Sergey Brin.

Musk responded, where else, on Twitter, denying the report, which cited unidentified sources, saying "Sergey and I are friends and were at a party together last night! I've only seen Nicole twice in three years, both times with many other people around. Nothing romantic."