WASHINGTON (AP) — President Joe Biden on Sunday ordered an "unidentified object” shot down with a missile by U.S. fighter jets Sunday over Lake Huron, and it was believed to be the same one tracked over Montana and monitored by the government beginning the night before, U.S. officials said.

The downing came after earlier objects over Alaska and Canada were shot out of the sky because they were flying at altitudes that posed a threat to commercial aircraft, according to the officials, who had knowledge of the downings and spoke to The Associated Press on condition of anonymity to discuss the sensitive operations.

It was extraordinary that four objects were shot out of the sky by U.S. fighter jets in eight days. Pentagon officials have said they don’t know when the last shootdown of an unknown or unauthorized object over U.S. territory occurred.

The latest object brought down was first detected on Saturday evening over Montana, but it was initially thought to be an anomaly. Radar picked it up again Sunday hovering over the Upper Peninsula of Michigan and it was going over Lake Huron.

U.S. and Canadian authorities had restricted some airspace over the lake earlier Sunday as planes were scrambled to intercept and try to identify the object. The latest object was octagonal, with strings hanging off, but had no discernable payload. It was flying low at about 20,000 feet, according to one senior U.S. official.

U.S. officials were still trying to precisely identify the other two objects blown from the sky by F-22 fighter jets over the past two days. They also were working to determine whether China was responsible as concerns escalated about what Washington said was Beijing's large-scale aerial surveillance program.

The object shot down Saturday over Canada's Yukon was described by U.S. officials as a balloon significantly smaller than the balloon — the size of three school buses — hit by a missile Feb. 4 while drifting off the South Carolina coast after traversing the country. A flying object brought down over the remote northern coast of Alaska on Friday was more cylindrical and described as a type of airship.

On May 5, 1945, six civilians were killed near Bly, Oregon, when they discovered one of the balloon bombs in Fremont National Forest, becoming the only fatalities from enemy action in the continental U.S. during the war.

Reverend Archie Mitchell and his pregnant wife Elsie (age 26) drove up Gearhart Mountain that day with five of their Sunday school students for a picnic. While Archie was moving the car, Elsie and the children found the balloon and carriage, loaded with an anti-personnel bomb, on the ground. A large explosion occurred; the four boys (Edward Engen, 13; Jay Gifford, 13; Dick Patzke, 14; and Sherman Shoemaker, 11) were killed instantly, while Joan Patzke (13) and Elsie died shortly afterwards. A bomb disposal expert guessed that the bomb had been kicked or otherwise disturbed. Military personnel who arrived on the scene observed that the balloon had snow beneath it, unlike the surrounding area, and concluded that it had lain there undisturbed for weeks until discovered. The U.S. press blackout was lifted on May 22 so the public could be warned of the balloon threat.