WASHINGTON (AP) — Special counsel Robert Mueller is scrutinizing the connections between President Donald Trump's campaign and the data mining firm Cambridge Analytica.

Cambridge Analytica has come under fierce criticism from U.S. and British lawmakers over reports it swiped the data of more than 50 million Facebook users to sway elections.

Mueller's investigators have asked former campaign officials about the Trump campaign's data operations, particularly how it collected and utilized voter data in battleground states.

That's according to a person with direct knowledge of the line of inquiry who isn't authorized to discuss the matter publicly and spoke on condition of anonymity.

The Trump campaign has distanced itself from the firm. It was financed by major Republican donors and, for a time, employed Steve Bannon, who later became Trump's campaign chief executive.