Grand jury investigations are "meant to remain secret," so the news that special counsel Robert Mueller had empaneled a grand jury to investigate allegations into Russian interference had to have been leaked, White House counselor Kellyanne Conway said Friday.

"It could be anybody that's on the grand jury," Conway told Fox News' "Fox & Friends" program. "It could be one of the lawyers; it could be anyone, I suppose."

The Wall Street Journal, quoting sources close to the matter, first reported Mueller was using a grand jury as part of the investigation. The grand jury is separate from one being used in Alexandria, Va. to gather information on former national security adviser Michael Flynn.

Prosecutors often use grand juries in criminal investigations, and the use of one suggests Mueller and his investigative team will demand documents and subpoena witnesses as the probe continues. However, the presence of a grand jury does not suggest criminal charges are pending, or if they'll be sought.

"Let me remind everyone what the president has said about this," said Conway. "It's a witch-hunt. It's fake. Last night I believe he called it a fabrication."

Such investigations, she continued, become "fishing expeditions" in which prosecutors throw information against a wall in hopes it will stick.

The Trump administration has agreed to comply and share what information it could, she said, including with son-in-law and senior adviser Jared Kushner's meeting last week with House and Senate officials.

"You have heard Don Jr. say he would share information he has" about a meeting involving a Russian attorney, she continued.

"What came of that meeting?" she said. "There was no consequence, no follow-up, no smoking gun. I became the campaign manager shortly after that."

Trump, she continued, defeated Democratic nominee Hillary Clinton by being a better candidate "who connected with people and didn't seem angry all the time."

Conway, however, said that "really what should concern everyone are those leaks that imperil national security," such as the leaks of President Donald Trump's phone calls with the president of Mexico and Australia's prime minister, The Washington Post reported on Thursday.

"Leaking the phone calls between our president and other heads of state is nothing short of a national disgrace," Conway said. "You know who agrees with that? Democratic senator from Virginia Mark Warner.

"He said so yesterday. He said governors, senators and indeed, presidents of the United States need to have confidence that they can engage in conversation with other heads of state. They can negotiate. They can discuss issues without the threat of it being leaked."

Conway, though, said the West Wing is a "small place" and that it will be "easier to figure out who is leaking than the leakers may realize. On this matter, I want there to be bipartisan outrage because we need people who understands this imperils national security."