US Congressmen have demanded an explanation from Facebook over violations of the social networking Web site's privacy rules. It was revealed earlier that applications within Facebook released user information to web tracking companies.

Republican Congressman Joe Barton from Texas and Democratic congressman from Massachusetts, lodged 18 questions to Facebook founder Mark Zuckerberg over what has been termed a "privacy breach."

In an earlier blog post, Facebook engineer Mike Vernal admitted that third-party application in the Web site had released user identification (UID) information.

"Nevertheless, we are committed to ensuring that even the inadvertent passing of UIDs is prevented and all applications are in compliance with our policy... Our policy is very clear about protecting user data, ensuring that no one can access private user information without explicit user consent," Vernal said.

"We take strong measures to enforce this policy, including suspending and disabling applications that violate it."

The two congressmen, who co-chair the House BiPartisan Privacy Caucus, released a letter for Web site. The letter read: "Given the number of current users, the rate at which that number grows worldwide, and the age range of Facebook users, combined with the amount and the nature of information these users place in Facebook's trust, this series of breaches of consumer privacy is a cause for concern."