FCC Chairman Brendan Carr informed Comcast on Tuesday that he has launched an investigation into the company’s relations with its NBC affiliates, days after President Trump called for the network to be held “accountable” for favoring the Democratic Party and threatened to revoke broadcast licenses.

The letter, dated Tuesday and released publicly Wednesday, was addressed to Comcast CEO Brian Roberts. In it, Carr, who was appointed by President Donald Trump, said he had directed the FCC’s Media Bureau to conduct the inquiry to “ensure compliance with FCC regulations as well as the public interest standard.”

The chair of the Federal Communications Commission is opening a probe into NBC-parent Comcast’s relationships with its local broadcast TV affiliates, the latest in a series of investigations into major U.