People who use social-media websites such as Facebook and LinkedIn may have their information harvested by companies that collect, analyze or sell consumer data, a group of U.S. lawmakers said Thursday.

Acxiom Corp.; Epsilon Data Management LLC, a unit of Alliance Data Systems Corp.; and Intelius Inc. are among those saying they collect publicly available social-media information, in response to questions sent by a group of House members, including G.K. Butterfield of North Carolina. 

Representatives Ed Markey and Joe Barton lead the group.

“Posting to Facebook should not also mean putting personal information into the hands of data reapers seeking to profit from details of consumers’ personal lives,” Markey said in an e-mail. “Users of social media want to share with friends, not enable the sale of their personal information to data miners.”

The lawmakers said the companies’ responses offer “only a glimpse” of the practices of multibillion-dollar data brokerage industry. Many questions remain unanswered, including “how they analyze personal information to categorize and rate consumers,” they said.

Markey, a Massachusetts Democrat, and Barton, a Texas Republican, on July 24 sent letters to companies including Equifax Inc., Experian Plc and Fair Isaac Corp., the company that developed the FICO consumer credit rating score.

Markey and Barton lead the Congressional Bipartisan Privacy Caucus.

Other House members signing the letters were Democrats Henry Waxman of California, G.K. Butterfield of North Carolina, and Bobby Rush and Jan Schakowsky of Illinois, and Republicans Steve Chabot of Ohio and Austin Scott of Georgia.