SAN FRANCISCO — Morrison & Foerster revealed in a filing in federal court Wednesday that it accidentally kept copies of some documents from Anthony Levandowski, the star engineer accused of having stolen over 14,000 files from Google's self-driving car division Waymo.

It is not clear whether any of the files that MoFo has in its possession are actually from Waymo, or whether they contain stolen trade secrets. MoFo said it does not know the contents of the “vast majority of these documents,” or whether they respond to a court order directing all files stolen from Waymo to be returned to the company.

The filing comes in response to demands made last week by U.S. District Judge William Alsup of the Northern District of California that MoFo answer why it should not be found in violation of his earlier order regarding Waymo's files.