The Justice Department has launched an antitrust investigation into five of America’s biggest television networks, including Fox News and CNN, over allegations they coordinated a boycott of President Donald Trump’s White House events.

Federal officials are investigating whether ABC, CBS, CNN, NBC and Fox News broke competition laws when they collectively suspended their shared television coverage of the president after his administration barred CNN journalists from the White House.

The escalation in Trump’s increasingly bitter war with the media could expose some of the country’s most powerful news organizations to legal scrutiny over their decision to stand together against restrictions imposed on one of their competitors.

Justice Department officials contacted the networks on Friday, demanding internal communications and documents relating to their joint coverage arrangements, according to six people familiar with the investigation who spoke to The New York Times.

The inquiry centers on the White House television pool, a decades-old arrangement under which broadcasters take turns recording presidential events and distributing footage to other news organizations.

But the system descended into chaos last month after Trump moved to restrict access for CNN, Politico and MS NOW, accusing the outlets of unfairly negative reporting.

The five television networks responded by temporarily suspending their pooled coverage of the president, leaving some major White House events without the usual shared footage.

Among the affected occasions was Trump’s meeting with Chinese President Xi Jinping, during which footage of the two leaders greeting one another was not broadcast through the major networks’ usual pool arrangement.

The apparent show of solidarity infuriated Trump, who accused the broadcasters of deliberately refusing to cover what he regarded as a historic diplomatic occasion.

Now, the Justice Department is examining whether their collective decision amounted to an illegal agreement among commercial competitors.

In a statement on Saturday, department spokeswoman Emily Covington accused the networks of having ‘proudly boycotted covering White House events.’

‘Group boycotts among commercial competitors can violate the Sherman Act,’ Covington said.

‘The Antitrust Division is simply investigating to determine whether these news organizations have violated the antitrust laws.’

The Sherman Act, one of America’s principal antitrust statutes, prohibits certain agreements between businesses that unlawfully restrain competition.

Although television networks routinely compete for viewers, advertising revenue and exclusive coverage, they have long cooperated through the White House pool to ensure presidential events are recorded and made available to the wider press.

The investigation raises the contentious question of whether that cooperation crossed a legal line when the networks collectively withdrew their services in protest over restrictions on CNN.

According to the Times, officials have been discussing a possible investigation for at least a week.

The inquiry remains in its preliminary stages and is being overseen by the Justice Department’s civil division, headed by Associate Attorney General Stanley Woodward, a former White House lawyer.

Letters sent to the networks Friday sought communications between executives and other officials concerning their decisions about pool coverage.

Investigators also requested correspondence relating to the administration’s withdrawal of CNN’s access to parts of the White House operation.

The move comes after weeks of escalating confrontation between Trump and journalists covering his second presidency.

On September 18, the president barred CNN, Politico and MS NOW from the White House grounds, citing what he described as ‘purposely negative stories.’

The three organizations challenged the restrictions in federal court, arguing that the administration had violated their First Amendment rights.

Trump’s administration defended its position by insisting that access to the White House was a ‘privilege’ rather than an unconditional right.

A federal judge subsequently issued a temporary order restoring the organizations’ access, but it appears the dispute was far from over.

Although CNN journalists were again permitted onto the White House campus, administration officials continued preventing the network from carrying out its scheduled television pool responsibilities when Trump traveled aboard Air Force One.

The other major networks eventually resumed their individual pool duties on September 25.

However, the shared television feed has continued to disappear on occasions when CNN would ordinarily have been responsible for providing coverage.

Trump made his frustration clear after the interruption affected coverage of his engagements with Xi.

Writing on social media, the president complained that some news organizations ‘refused to cover one of the Biggest and Most Beautiful Events to take place in many years.’