The Department of Justice is adding to Uber’s woes.

The beleaguered ridesharing platform provider is now reportedly being probed for its use of “Greyball,” a program that helped Uber hide its drivers from local transport regulators. The criminal inquiry was first reported by Reuters, who specified that it wasn’t clear what—if any—crimes Uber allegedly committed.

After “Greyball” was unveiled in March, the tech firm restricted the use of the program, which loaded an alternate version of the Uber app onto the phones of suspected regulators in cities where it wasn’t officially licensed to operate. Instead of getting the same experience as other customers, regulators’ phones were allegedly flooded with false information regarding the availability of cars. This policy was put in place to deceive local officials and prevent them from impounding cars and fining drivers by hailing them through the app.

The controversial use of Greyball was uncovered by the New York Times, which said Uber identified potential law enforcement officials by studying customers’ credit cards for hints it might be tied to a police credit union, for example. Uber’s legal team reportedly OKed the move, though some within the company had ethical qualms.

Following the Times’ report, Uber said in a blog post that the technology was used for numerous purposes, including fraud prevention and deterring users who violated its terms of service. “We have started a review of the different ways this technology has been used to date…we are expressly prohibiting its use to target action by local regulators going forward,” wrote Joe Sullivan, Uber’s chief security officer.

Uber didn’t immediately return a request for comment. The Silicon Valley unicorn has been under heavy fire lately for reasons ranging from an alleged culture of misogyny, claims that it infringed the privacy of its customers by tracking them without permission, and reportedly overcharging some customers.