But the full scale of the data leak involving Americans has not been previously disclosed — and Facebook, until now, has not acknowledged it. Interviews with a half-dozen former employees and contractors, and a review of the firm’s emails and documents, have revealed that Cambridge not only relied on the private Facebook data but still possesses most or all of the trove.

Cambridge paid to acquire the personal information through an outside researcher who, Facebook says, claimed to be collecting it for academic purposes.

During a week of inquiries from The Times, Facebook downplayed the scope of the leak and questioned whether any of the data still remained out of its control. But on Friday, the company posted a statement expressing alarm and promising to take action.

“This was a scam — and a fraud,” Paul Grewal, a vice president and deputy general counsel at the social network, said in a statement to The Times earlier on Friday. He added that the company was suspending Cambridge Analytica, Mr. Wylie and the researcher, Aleksandr Kogan, a Russian-American academic, from Facebook. “We will take whatever steps are required to see that the data in question is deleted once and for all — and take action against all offending parties,” Mr. Grewal said.

Alexander Nix, the chief executive of Cambridge Analytica, and other officials had repeatedly denied obtaining or using Facebook data, most recently during a parliamentary hearing last month. But in a statement to The Times, the company acknowledged that it had acquired the data, though it blamed Mr. Kogan for violating Facebook’s rules and said it had deleted the information as soon as it learned of the problem two years ago.

In Britain, Cambridge Analytica is facing intertwined investigations by Parliament and government regulators into allegations that it performed illegal work on the “Brexit” campaign. The country has strict privacy laws, and its information commissioner announced on Saturday that she was looking into whether the Facebook data was “illegally acquired and used.”