Elon Musk may be in trouble again over a tweet.

On Monday (February 25), the U.S. Securities and Exchange Commission asked a judge to hold the Tesla CEO in contempt saying the billionaire violated last year's court order that required Musk to seek pre-approval of any written communications including social media posts that had information material to Tesla or its shareholders.

The SEC pointed to this tweet from Musk posted last week that says "Tesla made 0 cars in 2011, but will make around 500k in 2019." The regulator said it breached a settlement reached last year over this tweet in which Musk said he could take Tesla private at $420 dollars a share and that the funding had been secured.

The SEC said that amounted to fraud and settled with Musk, who paid a $20 million dollar fine and was ordered step aside as Tesla's chairman for three years.

The electric car company also had to pay $20 million.

It's not yet clear what the latest motion from the SEC could mean for Musk or Tesla.

But in a response by Tesla and Musk's lawyer disclosed by the SEC, the half a million unit production number was already communicated during the company's fourth quarter earnings call.

And Musk subsequently clarified his tweet to say that the "annualized production rate" at end of 2019 would probably be about 500,000, with deliveries expected to be about 400,000.

The news on Monday sent shares of Tesla down roughly five percent in after hours trading.