US lawmakers have invited Apple, Facebook and Google to attend a hearing on mobile phones and privacy on Thursday -- the second Capitol Hill appearance in a week for executives from Apple and Google. Senator Jay Rockefeller said the hearing of the Senate Consumer Protection, Product Safety and Insurance Subcommittee would focus on \"industry practices with respect to online mobile data collection and usage.\" \"The hearing will also explore the possible role of the federal government in protecting consumers in the mobile marketplace and promoting their privacy,\" the Democrat from West Virginia said. Among those listed as witnesses are Catherine Novelli, Apple\'s vice president for worldwide government affairs, Bret Taylor, Facebook\'s chief technology officer, and Alan Davidson, Google\'s director of public policy for the Americas. Davidson appeared before the Senate Judiciary Subcommittee on Privacy, Technology and the Law on May 10 along with an Apple executive, Bud Tribble, vice president for software technology at the California gadget-maker. During that hearing, Senator Patrick Leahy expressed \"deep concern\" about reports that Apple iPhones and Google\'s Android phones were \"collecting, storing, and tracking user location data without the user\'s consent.\" Davidson and Tribble both said their respective companies were committed to privacy protection and were not tracking their users. Tribble said popular location-based services on mobile devices such as the iPhone and iPad do require some data collection, however, and users are able to opt out if they wish with easy-to-use tools. Davidson stressed that \"location-sharing on Android devices is strictly opt-in for our users, with clear notice and control.\"