NEW YORK (CNNMoney) -- You can add two influential members of Congress to the list of people upset with Facebook over the social network's latest privacy flap.
Reps. Ed Markey of Massachusetts and Joe Barton of Texas fired off a letter to the Federal Trade Commission on Wednesday, asking for an investigation of Facebook's business practices.
In the letter, Markey and Barton take issue with Facebook's practice of gathering information about the websites its users visited even after users logged out.
"We believe that tracking users without their knowledge or consent raises serious privacy concerns," the letter said.
"When users log out of Facebook, they are under the impression that Facebook is no longer monitoring their activities. We believe this impression should be the reality," Markey and Barton added.
Earlier this week, an Australian tech blogger reported that even after logging out of Facebook, the website was collecting information about websites visited by the user.