NEW YORK — As advertisers flee Bill O’Reilly’s show amid mounting allegations of sexual harassment, Fox News parent 21st Century Fox is investigating one of those claims against its popular TV host.

The investigation is in response to a complaint lodged last week by Wendy Walsh, formerly a regular guest on Fox News’ “The O’Reilly Factor” show.

“21st Century Fox investigates all complaints and we have asked the law firm Paul, Weiss to continue assisting the company in these serious matters,” the company said.

Walsh and her lawyer, Lisa Bloom, had a two-hour phone interview with four Fox News lawyers. Bloom’s pronouncements came after a report by The New York Times that five women had been paid $13 million to settle allegations of sexual harassment or other inappropriate conduct by the host.