Elon Musk is under a US federal investigation related to his takeover deal for Twitter Inc.

The social media company announced the development in a court filing made public on Friday.

Twitter said it requested that Mr Musk’s lawyers produce their communications with federal authorities months ago but they had not done so, and asked a Delaware judge to order the lawyers to provide the documents.

In late September, Mr Musk’s lawyers provided a “privilege log” identifying documents to be withheld from discovery.

The log referenced drafts of a May 13 email to the US Securities and Exchange Commission and a slide presentation to the Federal Trade Commission, Twitter said.

A lawyer for Musk did not immediately respond to a request for comment.

The court request was filed on October 6, the same day the court granted a stay of litigation to allow Twitter and Mr Musk to close the $US44 billion ($70 billion) takeover deal.

The SEC has questioned Mr Musk’s comments about the Twitter acquisition.

In April, the SEC asked Mr Musk whether the disclosure of his nine per cent Twitter stake was late and why it indicated that he intended to be a passive shareholder.

Mr Musk later refiled the disclosure to indicate he was an active investor.

In June, the SEC asked Mr Musk in a letter whether he should have amended his public filing to reflect his intention to suspend or abandon the deal.