Several New York Times journalists were subpoenaed to testify under oath after they reported on alleged safety problems related to President Donald Trump’s new Air Force One plane, the US newspaper reported.

Federal agents delivered subpoenas to the journalists’ homes demanding that they appear before a federal grand jury investigating a possible crime, the Times said.

The newspaper had published articles alleging that the plane gifted by Qatar was not safe enough, and the Secret Service urged Trump to change planes on his way home from a NATO summit in Turkey.

The Department of Justice told the BBC it was investigating illegal leaks, adding: “Journalists are not the target, but those who leak classified information.”

David McCraw, the Times’s chief editorial lawyer, called the subpoena a “brazen act” and “nothing more than an attempt to prevent the public from knowing what is happening in their country by intimidating journalists from doing their jobs.”

The subpoenas — a legal requirement by a court or government agency that compels a person to appear or produce records or evidence — say the journalists’ testimony is necessary “with respect to an alleged violation of federal criminal law,” the Times reported.

The subpoenas require the journalists to appear before a grand jury in Manhattan on Wednesday, the Times said. Grand juries are made up of members of the public and convened by the U.S. government to examine evidence and decide whether there is enough to charge a person or people with a crime.

The New York Times reported security concerns about the president’s plane, citing anonymous sources. While speaking to the media about classified information is a crime, the United States Constitution protects the freedom of the press to report information of public interest.

“We value and appreciate the important role the press plays in this country, but the Department of Justice also plays an important role in ensuring that the people entrusted with our nation’s secrets do what they are supposed to do with that information, which means not sharing classified information,” the Department of Justice (DoJ) said in a statement provided to the BBC.

The Times reported Wednesday that while Trump flew to the NATO summit in Turkey on the new Air Force One, he left the summit on an older plane on the advice of the Secret Service. The next day, the newspaper reported that security officials were concerned that the newest plane did not have advanced safety features, including anti-missile capabilities.

“Our journalists report the facts and promote the right of the American public to know how their government is operating and how taxpayer money is being used,” said McCraw, the Times attorney.

Other outlets published similar reports, including CBS News, the BBC’s US news partner. A former US government official told CBS there was not enough time or money to upgrade the plane to the safety requirements to serve as Air Force One.

As these reports emerged, tensions with Iran over a negotiated ceasefire agreement were rising and the United States was launching attacks.