PORTLAND, Ore. (Reuters) - The city of Portland, Oregon, on Wednesday directed its attorneys to issue a subpoena intended to force Uber Technologies Inc to disclose software that helped its drivers evade local transportation authorities.

The logo of Uber is seen on an iPad, during a news conference to announce Uber resumes ride-hailing service, in Taipei, Taiwan April 13, 2017. REUTERS/Tyrone Siu

Uber has acknowledged using the software, known as Greyball, to circumvent government officials who were trying to clamp down on Uber in areas where its service had not yet been approved, including Portland. The company has since stopped the use of the software for that purpose, saying the program was created to check ride requests to prevent fraud and safeguard drivers.

Portland began investigating Greyball after The New York Times revealed its existence in March. Uber has shared some information with the city but has not turned over the Greyball software itself.

At a meeting on Wednesday, the Portland city council voted unanimously to direct the city attorney’s office to subpoena Uber for information the company has not turned over.

Commissioner Chloe Eudaly said she has had longstanding concerns about Uber attempting to flout local transportation laws.

“I think it’s time for them to see how far they can push,” she said.

An Uber spokesman could not immediately be reached for comment. Previously, the company said it had cooperated with the city and provided relevant information to its investigation.

Reuters reported last week that the U.S. Department of Justice has begun a criminal investigation into Uber’s Greyball program and that a Northern California grand jury had issued a subpoena to Uber concerning how the software tool functioned and where it was deployed.

Portland received its own subpoena from the Northern California grand jury for records relating to Uber’s activities, including emails between the city and the company or its representatives, according to a copy of the document reviewed by Reuters.

A subpoena from a grand jury is a request for documents or testimony concerning a potential crime. It does not, in itself, indicate wrongdoing or mean charges will be brought.