The city of Portland, Oregon has found that Uber used software to deliberately evade government officials whose job it was to regulate the company.

The Portland Bureau of Transportation said that in December 2014, when Uber did not have any permits, it used its so-called ‘Greyball’ software to block 17 rider accounts – 17 of which belonged to government officials – and deny 29 ride requests by city transportation enforcement officers.

Greyball allowed Uber to ignore or cancel ride requests from locations near enforcement agencies and from accounts with credit cards believed to be belonging to government workers. Uber stopped using the software in April 2015, once it gained its permit to operate.

Despite being found to be in breach, the city decided not to impose any penalties on the ride hailing company. The US Department of Justice allegedly began investigating Uber earlier this year for its use of the software.

“We have ensured that no attempts to evade regulators or deny service to riders” will be allowed in the future, Portland City Commissioner Dan Saltzman told Reuters in a statement.