US military-shot down objects are mysterious.

(BBC) ⸻ The US military is unsure what three flying objects it shot out of the skies over North America were - and how they were able to stay aloft. The fourth object, shot down over Lake Huron in Michigan near the Canadian border, was described as an unmanned "octagonal structure" with strings attached to it. It was downed by a missile fired from an F-16 fighter jet at 14:42 local time (19:42 GMT). The incident raises further questions about the spate of high-altitude objects that have been shot down over North America this month. US Northern Command Commander General Glen VanHerck said that there was no indication of any threat. Speculation as to what the objects may be has intensified in recent days. On 4 February, a suspected Chinese spy balloon was downed off the coast of South Carolina after hovering for days over the US. China denied the object was used for spying and said it was a weather monitoring device that had blown astray. Since then, American fighter jets have shot down three further high-altitude objects in as many days. President Biden ordered an object to be shot down over northern Alaska on Friday, and on Saturday a similar object was shot down over the Yukon in north-western Canada. The US and Canada are still working to recover the remnants, but the search in Alaska has been hampered by Arctic conditions. One senior official told ABC News that the three most recent objects were likely weather devices and not surveillance balloons. The top Democrat in Congress, Debbie Dingell, has called for the White House and defence officials to provide more information about the objects, which are believed to be surveillance balloons. Democratic Senator Jon Tester has criticised the Biden administration for its handling of the first suspected spy balloon, and Defence Secretary Ben Wallace has said the UK will conduct a security review following the recent incidents in the US and Canada.