The Justice Department is investigating whether ABC, CBS, CNN, NBC and Fox News violated federal antitrust laws by briefly suspending their pooled coverage of President Trump last month.

Officials contacted the networks on Friday and requested communications and materials related to the White House television pool, according to multiple people familiar with the matter. The longstanding pool system rotates responsibility among the networks for providing video footage of the president to other outlets.

The suspension occurred after the White House barred journalists from CNN, MS NOW and Politico from the grounds, which prevented CNN from fulfilling its pool duties. The networks halted pool coverage for several days, leaving some presidential events, including a greeting with Chinese President Xi Jinping, without live television coverage from the major networks.

In a statement released Saturday, Justice Department spokeswoman Emily Covington said the networks had “proudly boycotted covering White House events.” She added that group boycotts among commercial competitors can violate the Sherman Act and that the Antitrust Division is examining whether the organizations broke the law.

The probe marks a significant escalation in tensions between the Trump administration and the press corps. The three excluded outlets sued the administration over the credential revocations, and a federal judge later ordered their reinstatement.

Network representatives have not issued public responses to the latest development. The inquiry focuses on the coordinated decision to stop providing shared footage rather than the underlying dispute over access.