In recent weeks, prosecutors questioned potential witnesses including former workers and banks that have conducted business with the firm, the New York Times reported on Tuesday, citing one US official and "other people familiar with the inquiry."
The report said the Justice Department and the FBI refused to comment on the matter.
Facebook on Monday said it suspended about 200 apps as it investigates the misuse of private data in the wake of the Cambridge Analytica scandal. In late March, media reported that the personal information of about 50 million Facebook users had been harvested by Cambridge Analytica during the 2016 US presidential campaign on behalf of the Trump campaign.
Earlier this month, the firm and its parent company SCL Elections announced that they would close their offices and declare bankruptcy in the United Kingdom and the United States.
