Three prominent U.S. lawmakers have asked Google (NASDAQ: GOOG) to answer questions about the inadvertent collection of wireless data traffic through its Street View program, continuing government scrutiny into an unwelcome privacy controversy for the search giant.

In a letter (PDF format) to Google CEO Eric Schmidt, Reps. Henry Waxman (D-Calif.), Ed Markey (D-Mass.) and Joe Barton (R-Texas) asked the company to provide information about the extent of its Street View operations in the United States and the procedures it has in place to safeguard personal information.

The rash of concerns about the Street View program followed Google's revelation that its camera-equipped cars -- dispatched to gather images of city streets -- also had been accidentally collecting Internet content sent over unsecured Wi-Fi networks.

Earlier this year, authorities in Germany, where the Street View program has been particularly controversial, had asked Google about the specific types of information it was collecting. At first, the company explained that in addition to images, its cars were collecting only basic Wi-Fi information, such as network names and equipment addresses.

At the request of German officials, Google then conducted an audit of its Wi-Fi data collection, only to find that since 2007, it had been snaring the actual contents of unsecured Internet traffic thanks to a piece of software that had been mistakenly been included in the cars' equipment.

The company has since said that it has been working with the relevant authorities to delete the unwanted data, but for many officials, including the congressmen who authored this week's letter, troubling questions remain unanswered.

"In particular, we are concerned that Google did not disclose until long after the fact that consumers' Internet use was being recorded, analyzed and perhaps profiled," the lawmakers wrote. "In addition, we are concerned about the completeness and accuracy of Google's public explanations about this matter."

The lawmakers also hinted at the possibility that Google could find itself on the wrong side of a variety of U.S. laws, including a 1986 statute prohibiting the intentional interception of electronic communications. A Google spokesman confirmed that since the errant software was included in the Wi-Fi equipment across its Street View fleet, the cars collected U.S. data transmissions, but dismissed any suggestions of criminal liability.

"As we have said before, this was a mistake," the spokesman told InternetNews.com in an e-mail. "Google did nothing illegal and we look forward to answering questions from these congressional leaders."

At the same time, authorities in several European countries have opened criminal investigations of the data-collection mishap, which burst on the scene at a time when many government officials and advocacy groups are taking a harder look at Internet privacy issues.

On Wednesday, the European Commission's privacy authority sent letters to Google, Microsoft (NASDAQ: MSFT) and Yahoo (NASDAQ: YHOO), warning the companies that their methods of anonymizing search don't comply with EU law, and asking that they enlist a third-party auditor to oversee with the process.

Jacob Kohnstamm, the chairman of the EC's Article 29 Working Party, also sent a letter to the chairman of the Federal Trade Commission asking whether the companies' policies might breach the section of U.S. trade law barring unfair or deceptive practices.

In the meantime, U.S. lawmakers have expressed concerns about other industry practices on the Internet privacy front. Facebook officials have been in talks with aides to several senators alarmed at some of the social network's recent changes to its privacy policies. Their inquiry was part of a broader backlash that prompted Facebook yesterday to announce a new set of privacy tools to enable users to more easily limit how their information is shared.

Earlier this year, a group of House lawmakers called on the FTC to launch an investigation into the privacy implications of Buzz, the search giant's new social networking service.

Similarly, two of the signatories to this week's letter, Markey and Barton, who co-chair the House Privacy Caucus, had earlier asked the FTC to investigate the Wi-Fi issue. Waxman, the chairman of the Energy and Commerce Committee, is a new addition to the inquiry.

The lawmakers asked Google to respond to the letter by June 7.

Kenneth Corbin is an associate editor at InternetNews.com, the news service of Internet.com, the network for technology professionals.