A federal grand jury has launched a probe into how popular smartphone apps share information, according to a SEC document filed Monday by Internet radio service Pandora.

In an update to its initial public offering, Pandora said it had been served with a subpoena to provide documents for a federal grand jury the company believed was investigating high-profile apps for Android smartphones and Apple iOS devices like the iPhone. 

“We believe that similar subpoenas were issued on an industry-wide basis to the publishers of numerous other smartphone applications,” Pandora said.

The scope of the investigation remains unclear.

Pandora said it believed the grand jury was looking into the “information sharing processes” of popular smartphone apps. The use of subscribers’ location information and personal data by apps and wireless operators has previously come under scrutiny from consumer advocacy groups and lawmakers. 

Neither Apple nor Google replied to requests for comment on the investigation. So far, no other app developers and publishers have come forward to say they also have been subpoenaed by the federal grand jury.

App developers use subscribers’ personal information, such as location, gender and personal preferences, to sell more targeted ads to mobile marketers.