Ridesharing startup Lyft has expanded its carpooling service to Los Angeles, despite warnings from the citys district attorney that the service may be illegal.

Lyft Line, the companys new service, has been rolled out in LA after launching in San Francisco last month, in defiance of district attorney Jackie Lacey, who joined with San Franciscos DA in alleging that ridesharing services are breaking the law and misleading consumers.

The two DAs sent a joint letter to Lyft and rival services Uber and Sidecar, warning that they were “prepared to file an action against [the businesses] seeking injunctive relief and civil penalties” should the companies not remove the ridesharing option from their services, as well as demanding they make clear on their website what sort of background checks were carried out on drivers.

Lyft has previously challenged the idea that ridesharing services violate the law, stating in a letter earlier in the month that the law being cited was “not written to prevent casual carpooling, which has been used by commuters for decades.”

In response to the new concerns raised by the district attorneys, a Lyft spokesperson spoke to the Wall Street Journal, saying: “Ridesharing has been enthusiastically embraced by California residents and we have worked closely with the California Public Utilities Commission over the past two years to secure a future for this innovative option throughout the state. We are confident that we can work with the District Attorneys offices to address the items outlined in their letter and look forward to discussing with them soon to do so.”