SAN FRANCISCO (Reuters) - A magistrate judge has ruled that Uber Technologies Inc [UBER.UL] must hand over a key document that could shed light on what its executives knew about alleged theft of trade secrets from Alphabet Inc's GOOGL.O Waymo self-driving car unit.

FILE PHOTO - A man arrives at the Uber offices in Queens, New York, U.S. on February 2, 2017. REUTERS/Brendan McDermid/File Photo

Alphabet’s Waymo claimed in a lawsuit earlier this year that former engineer Anthony Levandowski downloaded more than 14,000 confidential files before leaving to set up a self-driving truck company, which Uber acquired soon after.

The document in question is a due diligence report on Levandowski’s startup prepared by Uber during its acquisition talks with the firm in 2016.

Waymo has been seeking a copy of the report as part of its preparation for trial, but Uber has refused to turn it over, citing attorney-client privilege. The dispute was reviewed by a magistrate judge, who issued a ruling under seal earlier this week, meaning the outcome was known only to Uber and Waymo.

A U.S. federal judge, who is overseeing the case, made reference to the ruling in court on Wednesday, making it clear the magistrate judge had sided with Waymo.

“Are you appealing the ruling against you on the due diligence report?” U.S. District Judge William Alsup asked Uber’s lawyers in court in San Francisco on Wednesday.

Uber attorney Karen Dunn told Alsup the company will likely decide its next steps by tomorrow.

If Uber does not prevail on appeal, the due diligence report would be turned over to Waymo lawyers. It is unclear whether the entire report, or portions of it, would ultimately become public.

At a court hearing last month, Alsup said the report was a potential “treasure trove” that would shed light on what Uber executives knew of Levandowski’s actions.

Levandowski is not a defendant in the case, but his actions, and what Uber executives knew about them, are at the center of Waymo’s lawsuit. Uber denies it used any of Waymo’s trade secrets but has fired Levandowski. A trial is scheduled for October.

Spokespeople for Uber and Waymo declined to comment.