CBS News -- Facebook (FB) shares fell more than 7 percent Monday amid controversy over how Cambridge Analytica, which was hired by President Trump's 2016 campaign, was able to harvest personal data from .
The stock opened 5.2 percent lower, then slid to $171.27 by noon, a drop of 7.5 percent.
Facebook alleges that users' data was taken from its site using an unapproved method. The company said a researcher built an app that provided a personality quiz to Facebook users, but the social media giant claims the researcher then "lied to us" and passed the content onto Cambridge Analytica. That firm then used the data to build "psychographic profiles" about voters.
Massachusetts attorney general Maura Healey wrote on Twitter that her office is launching an investigation into the data usage. Politicians in both the U.S. and the U.K. are demanding that Facebook CEO Mark Zuckerberg explain how the data theft occurred and how the company plans to protect consumers.
"Massachusetts residents deserve answers immediately from Facebook and Cambridge Analytica," Healey wrote.
Sen. Richard Blumenthal, D-Connecticut, on Monday urged the Federal Trade Commission to investigate Facebook, in a tweet calling the company's policies to protect consumer data a "hollow promise." He also urged Congress to examine what he described as links between Cambridge Analytica and "Russian state interests."
Facebook suspended Cambridge Analytica over the weekend. The social network said it had removed the app in 2015 when it learned about the violation of its policies.
"Several days ago, we received reports that, contrary to the certifications we were given, not all data was deleted," Facebook deputy general counsel Paul Grewal wrote in a Friday post. "We are moving aggressively to determine the accuracy of these claims."