At least one wireless carrier in the United States has violated federal law by disclosing users’ real-time location data to third parties without permission, according to the Federal Communications Commission.

“I am writing to follow up on my letter of December 3, 2019 regarding the status of the FCC’s investigation into the disclosure of consumers’ real-time location data,” FCC Chairman Ajit Pai wrote in a letter. “Fulfilling the commitment I made in that letter, I wish to inform you that the FCC’s Enforcement Bureau has completed its extensive investigation and that it has concluded that one or more wireless carriers apparently violated federal law.”