Sunday, President Joe Biden told U.S. fighter jets to shoot down a “unidentified object” over Lake Huron. The object was thought to be the same one that had been tracked over Montana and watched by the government starting the night before, U.S. officials said.

Officials who knew about the downing’s and spoke to The Associated Press on the condition of anonymity to talk about sensitive operations said that earlier objects over Alaska and Canada had been shot out of the sky because they were flying at heights that made them a threat to commercial aircraft.

It was strange that U.S. fighter jets shot four things out of the sky in just eight days. Officials at the Pentagon have said that they don’t know when the last time was that an unknown or unauthorized object was shot down over U.S. territory.

The latest thing to be brought down was first seen over Montana on Saturday night, but at first it was thought to be a mistake. On Sunday, radar picked it up again as it was flying over Lake Huron and the Upper Peninsula of Michigan.

Sunday morning, U.S. and Canadian officials closed off some airspace over the lake while planes were sent to intercept and try to figure out what the object was. The most recent object was an octagon with strings hanging off of it, but it didn’t seem to have a clear payload. One top U.S. official said that it was flying low, at about 20,000 feet.

U.S. officials were still trying to figure out exactly what the other two things were that F-22 fighter jets had blown out of the sky over the past two days. As worries grew about what Washington said was Beijing’s large-scale aerial surveillance programme, they also tried to find out if China was to blame.

The object that was shot down over Canada’s Yukon on Saturday was called a balloon by U.S. officials. It was much smaller than the balloon that was hit by a missile on February 4 while drifting off the coast of South Carolina. That balloon was the size of three school buses. Friday, a round-shaped flying object was found on the remote northern coast of Alaska. It was said to be a type of airship.

Officials who talked to The Associated Press about the ongoing investigation on the condition of anonymity said that both were thought to have had a payload attached to them or hanging from them. Officials couldn’t say who sent the objects into the air and were trying to find out where they came from.

The three objects were much smaller and looked different than the suspected Chinese spy balloon that fell into the Atlantic Ocean after the U.S. missile strike. They also flew at lower altitudes.

The officials said that the objects in Alaska and Canada didn’t fit with the fleet of Chinese surveillance balloons that flew over more than 40 countries at least as far back as when Trump was president.

Late in January, that big white ball first showed up in the sky above the U.S. Since then, people have been glued to the sky. The U.S. government made it clear that they are always looking for unknown radar blips, and it is not unusual for them to close the airspace as a precaution while they figure out what they are. They would also act if they had to.

On Sunday, the U.S. closed the airspace over Lake Michigan for a short time. About an hour later, they opened it back up.

Chuck Schumer, who is the leader of the Senate’s majority party, said on ABC’s “This Week” that U.S. officials were working quickly to clean up the mess. He called the objects “balloons” as a shorthand way to describe them and said that U.S. military and intelligence officials were “focused like a laser” on gathering and collecting information, then putting together a full analysis.

“The bottom line is that we didn’t know about these balloons until a few months ago,” said Schumer, D-N.Y., about the spy programme that the administration has linked to China’s military, the People’s Liberation Army. “That we didn’t know is crazy.”

Eight days ago, F-22 jets brought down the big white balloon that had been floating over the U.S. for days at about 60,000 feet. U.S. officials immediately blamed China, saying that the balloon could move on its own and was set up to find and collect intelligence signals. Officials at the White House said that better surveillance helped find it.

China’s Foreign Ministry said that the unmanned balloon was a civilian meteorological airship that had gotten off course. Beijing said that the U.S. “overreacted” when it shot it down.

Then, on Friday, an object was found near Deadhorse, Alaska, which has a small population, and it was shot down by the North American Aerospace Defense Command. This is a joint U.S.-Canadian organisation that protects the airspace over both countries.

U.S. officials said that later that evening, NORAD found a second object flying high above Alaska. It flew into Canadian airspace on Saturday and was over the remote Yukon when Prime Minister Justin Trudeau gave the order to shoot it down.

In both cases, the objects were about 40,000 feet above the ground. On Sunday, the thing was flying at a height of 20,000 feet.

The cases have made diplomatic tensions between the US and China worse, raised questions about how much Beijing is being watched by the US, and caused Republican lawmakers to criticize the administration’s response for days.

Rep. Mike Turner, who is in charge of the House Intelligence Committee, said that the government seemed “a little too quick to pull the trigger.”

Turner, R-Ohio, said on CNN’s “State of the Union” that this is better than when the Chinese spy balloon was flying over some of the most sensitive sites and they let it happen.

After the shootdown last weekend, Chinese officials said they were ready to “take further actions” and criticized the U.S. for “an obvious overreaction and a serious violation of international practice.”

Rep. Jim Himes of Connecticut, who is the top Democrat on the House Intelligence Committee, asked the administration to be as open as possible. He said that the lack of solid information was fueling online rumors’.