The U.S. is investigating how customer data is used by some popular applications that run on the mobile platforms of Apple Inc and Google Inc.

Online radio service Pandora said in a regulatory filing on Monday it was subpoenaed by a Federal grand jury requesting information. It believes it is not the target of the investigation and that similar subpoenas were issued on an industry-wide basis to the publishers of numerous other smartphone applications.

The company did not disclose when it received the subpoena. The information was contained in an amended filing by Pandora ahead of a public offering of around $100 million expected later this year.

The Web radio company has more than 80 million registered users some of whom use mobile apps to access the music service beyond their personal computers.

Pandora, Apple and Google were not immediately available for comment.

There are concerns from privacy watchers that popular applications such as Pandora's can disclose critical information about a user such as location, gender and age.

More than 300,000 apps are available on Apple's App Store catalog, while Google's Android carries over 100,000 and is growing fast. Billions of apps have been downloaded by users for everything from social networking on sites such as Facebook and Foursquare to accessing personal bank accounts.

(Reporting by Yinka Adegoke; editing by Richard Chang and Andre Grenon)

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