It was downed over Lake Huron in Michigan at 2.42pm on Sunday on President Biden's orders.

An F-16 jet fired a missile at about 20,000ft amid concerns that its relatively low altitude and flightpath could be a danger to civilian planes.

It's the fourth incident in just over a week - and the third in as many days - after objects were shot down in Alaska and Canada on Friday and Saturday respectively.

Officials speaking anonymously to Reuters news agency declined to say what the latest object looked like - but a senior US official later described it as an octagonal structure.

They did not reveal whether it was manoeuvrable or just floating with air currents.

The Pentagon said the object had flown in proximity to sensitive US military sites and was regarded as a threat "due to its potential surveillance capabilities".

Congresswoman Elissa Slotkin tweeted that it had been "downed by pilots from the US Air Force and National Guard".

US and Canadian authorities restricted some airspace over the lake, near the Canadian border, before aircraft were scrambled to intercept and identify the object.

Earlier, the White House said the unidentified objects shot down over Alaska and Canada previously did not resemble the Chinese "spy" balloon downed near South Carolina a week ago.

A spokesperson for the National Security Council said they were "much smaller" but added: "We will not definitively characterise them until we can recover the debris, which we are working on."

Meanwhile, Canadian Prime Minister Justin Trudeau said recovery teams were searching for the object shot down over his country.

A US F-22 stealth jet brought it down on Mr Trudeau's orders on Saturday, over the mountainous and sparsely populated territory of Yukon in the northwest.

"Recovery teams are on the ground, looking to find and analyse the object," Mr Trudeau told reporters as he headed for the region.

"There's still much to know about it. That's why the analysis of this object is going to be very important."

Canada's defence minister Anita Anand described it as cylindrical, but said it was smaller than the Chinese balloon.

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It was flying at 40,000ft and posed a risk to civilian air traffic when it was brought down about 100 miles from the border at 3.41pm EST (8.41pm GMT), she added.

In the US, the Pentagon said that the North American Aerospace Defense Command (NORAD) had spotted the object over the coast of Alaska late on Friday.

Jets were scrambled from the state's Joint Base Elmendorf-Richardson and were joined by Canadian CF-18 and CP-140 aircraft after the object crossed into Canada.

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Pentagon spokesman Brigadier General Patrick Ryder said that the US F-22 had shot down the object using an AIM 9X missile "following close coordination between US and Canadian authorities".

Mr Trudeau said that the military will recover and analyse the wreckage, adding that he has spoken to US President Joe Biden and thanked NORAD for "keeping the watch over North America".

The White House said Mr Biden and Mr Trudeau would continue close coordination to "defend our airspace".

Earlier this week, Beijing admitted that the balloon shot down off South Carolina had come from China, but insisted it was a "civilian airship" that had strayed into American airspace and that it was for meteorological and other scientific research.