Apple Inc.’s iPhone and Google Inc.’s Android smartphones transmit location data from the handsets back to the companies, the Wall Street Journal reported, citing documents seen by the newspaper.

Apple “intermittently” collects information about iPhone users’ whereabouts, transmitting the data back to itself every 12 hours, the Journal reported, citing a letter it said the company sent to U.S. lawmakers last year.

Google’s Android phones send location data to the company several times an hour as well as information about local Wi-Fi networks and a code identifying the particular handset, according to the report. Google declined to comment, the Journal said.

Apple and Google may be using the data to study how to start providing location-based services, according to the report.