Democratic senators grilled senior Justice Department officials on Wednesday about why the agency issued subpoenas last week to several New York Times journalists, expressing concern that the Trump administration was threatening the freedom of the press.

The subpoenas, which in some cases were delivered by federal agents who showed up at reporters’ homes, sought to compel the journalists to testify before a federal grand jury in Manhattan. The reporters had recently published articles disclosing security concerns about President Trump’s new Qatari-donated Air Force One jet.

The coverage enraged Mr. Trump, and the White House quickly directed Kash Patel, the director of the Federal Bureau of Investigation, to oversee a leak investigation.

Shortly after the subpoenas were issued, The Times called them a “brazen” effort to intimidate its journalists from freely reporting on the actions of the federal government.

On Wednesday, Todd Blanche, the acting attorney general, whom Mr. Trump has nominated to lead the Justice Department, said at his Senate confirmation hearing that he had authorized the subpoenas.

“We’re not targeting reporters — they’re material witnesses,” he said in response to questions from Senator Peter Welch, Democrat of Vermont. “Just like a reporter would be a material witness to a car crash.”

Mr. Blanche acknowledged that federal officials hoped to ask the reporters about who had provided them with classified information concerning the president’s aircraft. Mr. Welch argued that it was “extremely important to protect the right of the press to have confidential sources.”

Typically, a leak investigation by the Justice Department would begin with a search for federal employees who could potentially have access to classified materials. Compelling a journalist to testify is often a last resort. In this case, the subpoenas were delivered days after The Times published its articles about the plane.

The subpoenas were issued by Jay Clayton, the U.S. attorney in Manhattan, who faced his own Senate hearing on Wednesday for his nomination to serve as Mr. Trump’s director of national intelligence.

At the hearing, Mr. Clayton offered few specifics about the matter, repeatedly saying the subpoenas were part of “an ongoing national security investigation.” He said that the U.S. attorney’s office had consulted with the Justice Department in Washington, and that he had followed “procedures that we have in place to protect the First Amendment, and protect the freedom of the press, and not result in intimidation of journalists.”

Senator Ron Wyden, an Oregon Democrat, was skeptical and asked Mr. Clayton if his office had made reasonable attempts to obtain information before subpoenaing the reporters.

“It was a consultative exercise with the career prosecutors in my office,” Mr. Clayton replied, adding, “We followed the process that we were required to follow.”

Senator Kirsten Gillibrand, a New York Democrat, described the U.S. attorney’s actions as “rough, aggressive, with an unnecessary urgency.” Mr. Clayton defended himself, saying that in matters of national security, he did not want government leakers to get away with disclosing classified information by exploiting the protections afforded to journalists.

Senator Michael Bennet, a Colorado Democrat, replied that the First Amendment was not a “loophole.”

In a video on Wednesday, Joe Kahn, The Times’s executive editor, described the subpoenas as “a naked attempt to intimidate The New York Times and to keep us from reporting on matters that we think are essential to national security.”

Mr. Kahn, a former China correspondent, said he had “seen the way an authoritarian government can keep journalists from reporting on a huge amount of news and information that’s very clearly in the public interest.”

“It’s really essential to American democracy that that kind of erosion of press freedoms not happen here,” Mr. Kahn said.