The US Congress is getting public about its concerns over privacy.
On Monday, the House Committee on Energy and Commerce released letters sent to Apple CEO Tim Cook and Alphabet CEO Larry Page inquiring how the companies protect users' privacy. Many of the questions for the executives were about mobile products, such as Apple's iPhone and the Android operating system made by Alphabet subsidiary Google.
The letters reference concerns that mobile devices track their users' whereabouts, even when they have taken precautions to prevent such monitoring. The committee was particularly interested in the possibility of offline data collection through location services, cellular towers, Wi-Fi hotspots and Bluetooth connection.
"Considering that many consumers likely believe that a phone that lacks a SIM card, or one for which they have affirmatively disabled location services, Wi-Fi, or Bluetooth -- such as through turning on 'Airplane Mode' -- is not actively tracking them, this alleged behavior is troubling," both letters read.
Lawmakers asked the companies to reply by July 23. Apple declined to comment and Alphabet didn't immediately respond to a request for comment.
The request for information comes amid mounting interest in privacy matters in Washington, which has been fueled by scandals at Facebook.
Follow the Money: This is how digital cash is changing the way we save, shop and work.
CNET Magazine: Check out a sample of the stories in CNET's newsstand edition.