Todd Spangler NY Digital Editor There’s a new wrinkle in the six-month-plus saga of Elon Musk’s mercurial attempt to buy Twitter. The multibillionaire is being investigated by federal authorities over his “conduct” in connection with his proposed Twitter acquisition, according to a letter from the company’s lawyers filed with the Delaware Chancery Court. The letter was filed Oct. 6 and released publicly Thursday. Twitter sued Musk in the Delaware court, demanding that he fork over the $44 billion he had agreed to under the binding pact reached in April. Twitter asserted that Musk’s legal team “exchanged substantive correspondence” with federal authorities — and that despite Twitter requesting copies of those documents “months ago” they had still not materialized. Twitter filed a motion seeking to have the court order Musk to produce the documents. Its letter cited drafts of a May 13 email to the SEC and a slide presentation to the FTC that Musk’s attorneys had identified as privileged documents.