Federal prosecutors are digging into Tesla’s use of company funds for a secretive project thought to center around building chief executive Elon Musk a giant glass home in Texas, The Wall Street Journal reported Wednesday. The project, referred to internally as “Project 42,” is being probed both by the U.S. Attorney’s Office for the Southern District of New York and the Securities and Exchange Commission. Both inquiries are in their early stages, with officials in both offices reportedly seeking information on the purpose of the project, how much Tesla spent on it, and any personal benefits paid out to Musk. The SDNY has also issued a number of subpoenas to current and former Tesla employees, some of whom are expected to appear in court in September, according to Bloomberg News. Project 42 was previously the subject of an internal board investigation at Tesla, the Journal reported in July, though the outcome of that probe is still unclear. That month, the newspaper reported that the “dramatic” glass building was set to be constructed near Tesla’s Austin gigafactory, and was internally understood to be a house for Musk, with some plans showing residential features.