The White House spokeswoman and top military officials on Tuesday said they had not yet found the remnants of the three objects shot down over the U.S. since Friday, meaning the military has yet to determine what they are.

"We just don't know," said White House press secretary Karine Jean-Pierre, amid questions from lawmakers, Americans and journalists about why the administration would shoot down the unprecedented number of objects within days without more knowledge.

A national security spokesman said the intelligence community is considering as a “leading explanation” that the objects could be “balloons tied to some commercial work.” The Biden administration has ruled out that they were owned by the U.S. government.

Joint Chiefs of Staff Chairman Gen. Mark Milley also confirmed earlier Tuesday that one of the missiles fired at an unidentified object flying above North America over the weekend missed its target.

Fox News first reported Monday, citing unnamed officials, that a missile fired at an octagonal object above Lake Huron on Sunday missed. CNN later confirmed the report.

During a news conference at NATO headquarters in Brussels that was largely focused on the Russia-Ukraine war, Milley acknowledged that one of the two missiles fired at the object missed. He said the missile landed “harmlessly” in Lake Huron. 

“We tracked it all the way down, and we made sure that the airspace was clear of any commercial, civilian or recreational traffic,” he said.

That object was the third shot down by U.S. fighter jets above North America in three days, and the fourth in eight days.

Asked by a reporter at the White House whether the president should be "embarrassed" that he may have shot down weather balloons or other benign devices, Jean-Pierre said no.

"I don't think the president should be embarrassed ... by the fact that he took action to make sure that our airspace, civilian airspace, was safe," she said.

Officials have noted the three objects were flying much lower than a larger surveillance balloon owned by China, in the altitude range of commerical planes.

Jean-Pierre would not respond to another question about whether the three missile takedowns were an overreaction, in response to bipartisan criticism of the president about his waiting to shoot down the spy balloon.

Officials added Tuesday that the decisions to shoot down the items were made with careful consideration of the safety of Americans on the ground.

In an appearance on CNN on Tuesday morning, John Kirby, spokesman for the White House National Security Council, would not confirm the missed shot, but when asked if he could guarantee Americans are on the ground are safe when such shots are fired, he said, “Yes, I can.”

“There are safety protocols with all these kinds of engagements,” Kirby said. “The whole purpose of these missions were to keep Americans safe. That's what was behind the president's decision from the very, very beginning — make sure that we're keeping the sky safe for civilian air traffic.”

Milley echoed that sentiment.

“We're very, very careful to make sure that those shots are in fact safe,” he said.

Kirby added the objects were “very small radar cross-section targets” and that “it's not inconceivable to me, as a former military man, to believe that one might have missed just because of the size of the target.”

U.S. officials said Tuesday that none of the debris from the three most recent incidents has been recovered. One object was shot down on Alaska’s northern coast, one in the Yukon in Canada and the other above Lake Huron, near Michigan. Milley said the object is probably “a couple hundred feet” deep in the lake.

“We'll get them eventually, but it's going to take some time to recover those,” Milley said.

On Feb. 4, a U.S. fighter jet shot down a suspected Chinese spy balloon off the coast of South Carolina. Debris from that incident has been recovered.

Officials say they do not yet know what the latest three objects were or what their purposes were. They’ve said the objects were not transmitting any communications signals. Intensive recovery operations are underway, Kirby said. 

In the CNN interview, Kirby said he believes that the North American Aerospace Defense Command’s decision to broaden the parameters of its radar surveillance could explain in part “why you've seen so many incidents in a short period of time.”

“The NORAD staff adjusted the parameters for the radar systems, the sensitivities, to look for things that were slow, high and small … in the wake of the Chinese spy balloon,” he said. “And so when you're doing that, when you adjust your sensitivities on the radar, you're likely to see more of those kinds of contexts.”

Kirby said the locations of the debris, particularly in Alaska and Canada, make the recovery efforts more difficult. 

“When you do something like this, you want to do it over areas where you're not going to hurt people on the ground, which means it's going to be over remote areas as best you can,” he said. “And then just getting to those remote areas can be difficult … particularly if you throw in not only the latitude at which these things are located — at least the first two — but the weather conditions right now. It's February, and up there near the Arctic, the weather conditions are just not real permissive for search and recovery operations.”

Meanwhile Tuesday, senior administration officials held a classified briefing for senators about the objects that were shot down.

Both Sens. Roger Marshall of Kansas, a Republican, and Richard Blumenthal of Connecticut, a Democrat, emerged from the meeting calling on the administration to disclose more to the public. 

"The president of the United States needs to get in front of the American public tonight and explain to them what we know,” Marshall said. 

"We walk out of a meeting like this, and so much of what we've been told is classified,” he added. “So I'm not going to be able to answer any of your questions now. But the president can get in front of America and tell them firsthand that we're safe, that everybody's going to be OK, that we've got this under control."

Said Blumenthal: "I have a better understanding, but the American people need and deserve to know more. 

"I am not in any way afraid that we are under a threat of attack or physical harm to our homeland,” he continued. “That's my personal feeling. But the American people need to be reassured with more fact."

Sen. Kevin Cramer, R-N.D., said he didn’t know if it was necessary “just yet” for Biden to address the nation. But, Cramer added: “Not addressing the nation fairly soon with straight-up facts and truth allows people's imagination to create something either far scarier or more benign than reality.”

Cramer said that after the briefing he’s “not any more concerned than I was before in terms of America's vulnerabilities.”

Senate Majority Leader Chuck Schumer, D-N.Y., said he thinks the Biden administration is “on top of this and done a very, very good job.”

“There's a lot of information to assess,” he said. “There's a lot of information to recover.”