The project is being investigated by federal prosecutors in Manhattan, as well as the Security Exchange Commission, the markets regulator, The Wall Street Journal reported this week.
Employees had complained to the Tesla's board about the project, known as Project 42, and that an internal investigation was carried out, the Journal said.
The plans called for a spacious glass building to be erected near the electric vehicle company's Austin-area headquarters,
The investigations were in their early stages and will not necessarily result in charges being made, the report said.
The Journal said Tesla employees were working on Project 42 last year.
Plans at one point included a building in the shape of a twisted hexagon, and images seen by the newspaper showed a large glass building that appeared to include living space.