Tesla's use of company funds on a secret project described internally as a house for Chief Executive Elon Musk, the Wall Street Journal reported on Wednesday, citing people familiar with the matter.
Neither Musk nor a spokesman for the U.S. Attorney's office in Manhattan, which the Journal said was carrying out the probe, immediately responded to requests for comment.
No dollar figures were disclosed, and the newspaper said the house was near Austin, Texas.
The Journal reported in July that Tesla board members had investigated whether company resources were misused on the effort.
The U.S. Securities and Exchange Commission has also opened a civil probe, the Journal reported.