In a Wednesday letter to both outlets, Carr said the inquiry would focus on whether the news organizations' member stations violated government rules by recognizing financial sponsors on air.

According to Carr, NPR and PBS stations operate as noncommercial broadcast organizations, but that they may be airing announcements that 'cross the line."

"I am concerned that NPR and PBS broadcasts could be violating federal law by airing commercials. In particular, it is possible that NPR and PBS member stations are broadcasting underwriting announcements that cross the line into prohibited commercial advertisements," Carr wrote.

"To the extent that these taxpayer dollars are being used to support a for-profit endeavor or an entity that is airing commercial advertisements," Carr wrote, "then that would further undermine any case for continuing to fund NPR and PBS with taxpayer dollars," the letter reads.

According to the report, station execs have been bracing for a potential battle with the Trump administration over government funding, and have been gaming out worst-case financial scenarioos.

Carr said he didn't see a reason for lawmakers to continue funding the organizations, adding that he planned to notify members of Congress of his findings, according to the NY Times.

NPR CEO Katherine Maher said in a statement that the organization's use of sponsorship - also known as underwriting, "complies with federal regulations."

"We are confident any review of our programming and underwriting practices will confirm NPR's adherence to these rules," she said. "We have worked for decades with the F.C.C. in support of noncommercial educational broadcasters who provide essential information, educational programming, and emergency alerts to local communities across the United States."

PBS also issued a statement, claiming to be proud of its "noncommercial educational programming," and that it had worked "diligently to comply with the F.C.C.'s underwriting regulations."