Apple Inc.'s iPhone is collecting and storing location information even when location services are turned off, according to a test conducted by The Wall Street Journal.

The location data appear to be collected using cellphone towers and Wi-Fi access points near a user's phone and don't appear to be transmitted back to Apple. Apple didn't immediately respond to a request for comment.

Still, the fact that the iPhone is collecting and storing location data—even when location services are turned off—is likely to renew questions about how well users are informed about the data being gathered by their cellphones. The fact that the iPhone stores months' worth of location data was disclosed by two researchers last week.

The discovery of an unencrypted location file on the iPhone created an uproar among people concerned that their phones could be searched and their location data used against them. On Saturday, Rep. Edward Markey (D., Mass.) called for a congressional investigation into the iPhone location storage, saying that unprotected location information on the phone could put children at risk from predators who hack their phones.

The discovery of the iPhone location file comes amid growing concern about cellphone tracking overall.

Last week, the Journal reported that Apple's iPhone and cellphones powered by Google Inc.'s Android software transmitted their locations back to Google and Apple, respectively.

Read more: Wall Street Journal