The US has shot down another unidentified object over its territory in the fourth military operation of its kind this month.
President Joe Biden ordered it to be downed near Lake Huron, close to the Canadian border, on Sunday afternoon.
The object could have interfered with commercial air traffic as it was traveling at 20,000ft (6,100m), a Pentagon statement said.
It was first detected above sensitive sites in Montana on Saturday, it added.
The object was described by defence officials as unmanned, octagonal in shape and not a military threat. It was downed by an F-16 fighter jet at 14:42 local time (19:42 GMT) on Sunday.
The incident raised further questions about the spate of high-altitude objects that have been shot down over North America this month.
A suspected Chinese spy balloon was downed off the coast of South Carolina on 4 February after hovering for days over the continental US. Officials later said it originated in China and had been used for surveillance.
China, however, denied the object was used for spying and said it was a weather monitoring device that had been blown astray. The incident – and the tense exchanges in the aftermath – ratcheted up tensions between Washington and Beijing.
Since that first incident, American fighter jets have shot down three further high-altitude objects in as many days.
On Friday, President Biden ordered an object to be shot down over Alaska. And on Saturday a similar object was shot down over the Yukon in north-western Canada.
Officials have not publicly identified the origin or purpose of these objects. Both the US and Canada are still working to recover the remnants, but the search in Alaska has been hampered by Arctic conditions.
“These objects did not closely resemble, and were much smaller than, the [4 February] balloon and we will not definitively characterise them until we can recover the debris,” a White House National Security spokesperson said.
Unidentified flying objects – timeline
4 February: US military shoots down suspected surveillance balloon off the coast of South Carolina. It had drifted for days over the US, and officials said it came from China and had been monitoring sensitive sites
10 February: US downs another object off northern Alaska which officials said lacked any system of propulsion or control
11 February: An American fighter jet shoots down a “high-altitude airborne object” over Canada’s Yukon territory, about 100 miles (160 km) from the US border. It was described as cylindrical and smaller than the first balloon
12 February: US jets shoot down a fourth high-altitude object near Lake Huron “out of an abundance of caution”
Earlier on Sunday, the top Democrat in Congress said intelligence officials believed the flying objects that were shot down on Friday and Saturday were also surveillance balloons.
“They believe they were [balloons], yes,” Senate Majority Leader Chuck Schumer told ABC News, adding that they were “much smaller” than the first one shot down off the South Carolina coast.
“The bottom line is, until a few months ago, we didn’t know of these balloons,” he said.
“We’re going to probably be able to piece together this whole surveillance balloon and know exactly what’s going on,” Mr Schumer added.
Democrat Debbie Dingell, one of several Michigan members of Congress who applauded the military for downing the object over the state on Sunday, said more information was needed on the flurry of similar incidents.
“We need the facts about where they are originating from, what their purpose is, and why their frequency is increasing,” she said.
Democratic Senator Jon Tester, who represents Montana, told the BBC’s US partner CBS: “What’s gone on the last two weeks or so… has been nothing short of craziness. And the military needs to have a plan to not only determine what’s out there, but determine the dangers.”
Republicans have criticised the Biden administration for its handling of the first suspected spy balloon, saying it should have been shot down far sooner.
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