Two Democratic senators have asked federal regulators to investigate the business practices of smart-television manufacturers amid worries that companies are tracking consumers’ viewing behavior without their knowledge.

In a letter on Thursday to Joseph Simons, the chairman of the Federal Trade Commission, Senators Edward J. Markey of Massachusetts and Richard Blumenthal of Connecticut said they were concerned about “consumer privacy issues raised by the proliferation of smart-TV technology.”

Companies are using new tools to identify and log what people are watching as part of an effort to profile consumers and direct ads to other devices in their homes. The letter cited a New York Times article, published last week, that detailed the practices of Samba TV, a San Francisco software company. Privacy advocates have criticized the company for not being transparent with consumers when it seeks permission to track their viewing on internet-connected TVs to sell ads.

“Regrettably,” the senators wrote, “smart-TV users may not be aware of the extent to which their televisions are collecting sensitive information about their viewing habits.” The letter went on to argue that Samba TV “does not provide sufficient information about its privacy practices to ensure users can make truly informed decisions.”