A U.S. Justice Department investigation of Fox News has widened to include a second law enforcement agency, according to a report late on Thursday from CNN.

The story, written by CNN's Brian Stelter, cites four sources close to the investigation as saying that financial crimes experts from the U.S. Postal Inspection Service have become involved in the probe. Postal authorities have jurisdiction over cases involving mail and wire fraud.

Both agencies have been involved in the investigation in recent weeks, Stelter reported.

Fox News has been under investigation since February regarding payments made for Fox News employees who charged the network's former chairman, Roger Ailes, with sexual harassment. Ailes was dismissed in July from the network he co-founded with 21st Century Fox (FOXA) - Get Fox Corporation Class A Report Executive Chairman Rupert Murdoch.

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One of the sources told CNN that investigators have been asking "how the shareholder money was spent; who knew; and who should have known."

Investigators have focused on whether confidants of Ailes were paid as consultants, and if so, what kind of work they were doing for the company, CNN reported. One of the consultants, Stelter wrote, earned $10,000 a month by submitting a monthly invoice to Fox.

The probe began under Obama Administration, but was only made public in February when attorney Judd Burstein, who represents some of Ailes' accusers, told reporters that the U.S. Attorney's Office for the Southern District of New York was conducting an investigation of Fox News.

Fox News' most popular anchor, Bill O'Reilly, was forced out of the company a week ago amid multiple allegations of sexual harassment.

A Fox News spokesman declined comment on the CNN story.