American lawmakers have expanded an investigation into the use of location-tracking systems on mobile devices. This follows recent reports about the storing of information on the Apple iPhone, iPad and iTouch. Questions have also been raised about Google Android devices. Some people consider location tracking to be a threat to personal privacy and security. Allan Friedman is the research director for technology and innovation at the Brookings Institution in Washington. He says all wireless companies do some amount of location tracking as part of their networks. Mr. Friedman says this information is usually stored by the companies, not the devices, and there are laws to protect it. He says: "Law enforcement, for example, has to have a fairly high standard before it can access that data. And the phone company is also prohibited from selling that information."Congress discussed the issue of mobile privacy last year. Now, two researchers reported that location tracking information is being stored directly on Apple devices. They said Apple's newest operating systems gather global positioning system and timestamp information. The information is stored on the device in a file that is also uploaded to any computer that the device is connected to. The researchers say the information is available to anyone who has access to the device or computer. Allan Friedman says applications that a user buys or get tricked into downloading might also be able to access this data and somehow misuse it.Apple said it is "not tracking the location of your iPhone." The company said the phone simply keeps a database of Wi-Fi hotspots and cell phone towers near the user's location. Apple said this is meant "to help your iPhone rapidly and accurately calculate its location when requested." In late April, leaders of the House Energy and Commerce Committee sent letters to some of the leading mobile device developers. These include Apple and Google. The letters asked for more information about their location tracking systems. Allan Friedman says there should be stronger controls over things like location data. He says we need to understand who is getting this information, how long are they keeping it and what exactly they are doing with it.

For VOA Special English, I'm Carol Presutti. For more stories about technology and for English teaching activities, go to voaspecialenglish.com.