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Reports of a hidden iPhone feature that silently tracks its users' whereabouts prompted widespread unease from smart phone customers Wednesday. Now, Capitol Hill lawmakers are demanding answers from Apple CEO Steve Jobs.

Researchers Alasdair Allan and Pete Warden on Wednesday released findings that Apple's iOS 4 software automatically tracks its users' locations, and stores that information in a file on iPhones and iPads. Privacy watchdogs say the unencrypted data could easily be compromised by third parties or hackers, especially when the devices are connected to a computer to "sync" music and other media.

"Anyone who gains access to this single file could likely determine the location of a user's home, the businesses he frequents, the doctors he visits, the schools his children attend, and the trips he has taken," Minnesota Democratic Senator Al Franken warned in a letter to Jobs. "There are numerous ways in which this information could be abused by criminals and bad actors."

Franken, recently named chair of a congressional subcommittee on privacy and technology, hinted that the iPhone software controversy could factor into hearings on Capitol Hill. "I haven't announced exactly when our first hearing is, but I will announce that very soon. And I certainly have been looking at mobile phones and privacy," Franken told home-state FOX affiliate KMSP.

Franken is asking Jobs to explain how and why Apple collects location data, citing concerns that "millions of children and teenagers" could be exposed to danger because of the tracking feature.

"I certainly don't know why they would allow it to unencrypted," Franken said of the data file. "People didn't know their whereabouts were being tracked all the time...and so part of the reason to have these hearings is so the public knows, and so we know, what these companies are doing, and to...keep our laws updated with the technology."

On the House side, Rep. Edward Markey, D-Mass., on Thursday sent his own letter to Jobs, asking that the CEO explain what he is doing to prevent harm to children and to detail whether or not Apple is using tracking information for a "commercial purpose." Markey has requested that Jobs respond to his letter by May 12. Washington Democratic Rep. Jay Inslee has also expressed concern over privacy violations.

"We have not gotten a response from them," Franken told KMSP of his letter to Jobs, adding that he had only just sent the letter the day before. "I hope to get a response very soon. I asked them a lot of questions."