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Days after the Electronic Privacy Information Center filed a complaint with the Federal Trade Commission about Facebook’s mood-tracking experiment, Sen. Mark Warner (D-Va.) is asking the agency to dig deeper into possible “ramifications” of the social network’s study.

“According to reports it’s not clear whether Facebook users were adequately informed or given an opportunity to opt-in or out,” Warner wrote in a letter to the FTC. “I also have concerns about whether or not Facebook responsibly assessed the risks and benefits of conducting this behavioral experiment as well as the ethical guidelines, in any, that were used to protect individuals.”

He goes on to say that the industry at large could stand to set some standards for future studies. He also thinks the FTC should consider possible oversight measures.

This is the latest response to Facebook’s emotional contagion study, which was recently released in the Proceedings of the National Academy of Sciences. Already the study is under investigation in U.K. and Ireland.

Facebook users and media outlets have also criticized the experiment, and Facebook has struggled to respond to it all. Facebook chief operating officer Sheryl Sandberg offered an apology for not notifying any of the 700,000 participants in the study. But last week Monika Bickert, the company’s global head of policy, called the study “innovation.”

Most recently, EPIC filed a complaint with the FTC, saying Facebook didn’t get consent from any the users it involved in its 2012 study, which violates an order of consent from 2012 and section 5 of the Federal Trade Commission Act regarding “deceptive acts or practices.”

At this point, the debate over the legality and ethics of study is far from over — it’s just heating up.

Here’s the letter from Warner:

Warner Letter to FTC 7 9 14

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