The US Department of Justice has allegedly begun investigating Uber’s use of a tool that helped its drivers avoid detection by local regulators in areas, like Portland, Oregon, where the service had not yet been approved.

Uber admitted to using ‘Greyball’, as the software is known, back in 2014 because it didn’t want its drivers to be penalised by authorities for operating without state approval – though has stated it was only used ‘sparingly’.

The company would prohibit the use of Greyball following the New York Times revealing its existence earlier this year. However, the ride hailing company claimed the program was created to check ride requests to prevent fraud and safeguard drivers.

It has now been revealed, according to Reuters sources, that the company could be facing criminal proceedings for the use of the software. Bloomberg BNA said last week that a California US attorney had launched a probe into Uber’s use of Greyball, according to a report from the Portland Bureau of Transportation.

The launch of criminal proceedings is just the latest in a long line of controversies and investigations that have been fired toward Uber over the last few months – all raising questions about CEO Travis Kalanick’s ability to lead the company and, often, criminal buccaneer actions.

It was recently revealed that the company had been using tracking software, called ‘Hell’, to keep an eye on its US ride hailing rival Lyft and its riders. And as a result of that software, Uber could also be facing even more legal cases against it.