Another day, another black eye for Uber.

The ride-sharing giant, reeling from revelations of a troubling workplace culture, is the subject of a new lawsuit from Waymo, previously known as Google's self-driving car project.

Waymo filed a suit against Uber Thursday, alleging a concerted plot to steal its trade secrets and intellectual property. The suit was filed in a federal court in California.

Waymo alleges that former employee Anthony Levandowski downloaded thousands of confidential files to a personal hard drive before resigning from the company. Levandowski then launched a self-driving truck company, Otto, which Uber purchased in 2016. Waymo also claims that other former employees now with Uber also downloaded confidential information.

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Waymo pursued the lawsuit after receiving an inadvertent email from a supplier that included a drawing of Uber's LIDAR circuit board. LIDAR is a type of laser sensor that is generally considered essential to developing a self-driving car. According to Waymo, the drawing of the circuit board had a striking resemblance to Waymo's own LIDAR.

Waymo notes that its engineers have spent thousands of hours developing the sensor, and it spent millions in the process.

"We didn't make this decision lightly," wrote Waymo, whose parent company Alphabet (GOOGL) is also an Uber investor through its Google Ventures arm. "However, given the overwhelming facts that our technology has been stolen, we have no choice but to defend our investment and development of this unique technology."

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The intense race to build self-driving cars has heated up lately. Waymo isn't the first to file a lawsuit involving a former employee and trade secrets. Earlier this year, Tesla sued the former director of its own self-driving car project, who left to launch his own startup.

Uber said in a statement that it takes the allegations seriously and will review the matter carefully.