The US Securities and Exchange Commission (SEC) is investigating Elon Musk's acquisition of Twitter, according to a court filing. The SEC is probing whether Musk violated federal securities laws when he bought stock in Twitter and made statements about the deal. The SEC is specifically interested in whether Musk disclosed his stake in Twitter promptly enough and whether he made false or misleading statements about his intentions for the company. The SEC investigation is a significant development, as it could lead to civil or even criminal charges against Musk. It could also delay or derail the Twitter acquisition.