A federal investigation into corporate practices at Fox News Channel may be widening, according to a report by CNN.

Federal prosecutors have for weeks been looking into whether or not past payments made to former female employees fox Fox News were properly disclosed or accounted for by the unit and its parent corporation, 21st Century Fox.. Now, according to the CNN report, personnel from the United States Postal Inspection Service are now involved in the matter. CNN cited four people familiar with the matter.

The Financial Times previously reported similar details.

A spokesperson for 21st Century Fox said he could not comment on the investigation. The company in February issued a statement noting that it had not received a subpoena from the U.S. Attorney’s office, but that it had “been in communication with the U.S. attorney’s office for months.” The company also said it “will continue to cooperate on all inquiries with any interested authorities. A Fox News spokesperson referred an inquiry to 21st Century Fox.

The federal probe is said to also be focused on potential misconduct by Fox News personnel and even “the overall environment at the network”, according to CNN.

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Since the departure of Roger Ailes, the former chairman and chief executive of Fox News, a number of settlements with former Fox News employees have been disclosed. Ailes was alleged by former Fox News anchor Gretchen Carlson and others to have sexually harassed several employees. Ailes has denied the charges.

Carlson agreed to a settlement last year believed to total as much as $20 million. Laurie Luhn, a former booker and event planner at Fox, is believed to have received a settlement coming to as much as $3 million after alleging a long pattern of harassment by Ailes, which he denied. A settlement between Fox News and former contributor Tamara Holder was revealed in March. Holder had levied sexual-harassment allegations against Francisco Cortes, a vice president of Fox News Latino, in October.

Since Ailes’ departure, a number of senior executives that helped run Fox News during his tenure have departed. Brigette Boyle and Nikole King, the senior vice president of recruitment for Fox News and Fox Business, and the senior vice president of business development and mobile for Fox News, respectively, departed in August. Tim Carry, who had been involved in negotiating distribution deals for both Fox News and Fox Business since their launches, announced his departure in November. Paul Rittenberg, who led ad sales for Fox News and Fox Business, announced his departure in February.