Canadian investigators are hunting for the wreckage of the mysterious flying object shot down by a U.S. fighter jet over Yukon territory, Prime Minister Justin Trudeau said Sunday, as the U.S. Senate's top lawmaker said that it - and another flying object shot down off the coast of Alaska - both appeared to be balloons.

"Recovery teams are on the ground, looking to find and analyze the object," Trudeau told reporters. He gave no hint as to what it was but said it "represented a reasonable threat to the security of civilian flight."

"The security of citizens is our top priority and that's why I made the decision to have that unidentified object shot down," he said.

North America has been on high alert for aerial intrusions following the appearance of a white, eye-catching Chinese airship over American skies earlier this month. The 200-foot-tall (60-meter-high) balloon - which Americans have accused Beijing of using to spy on the United States - caused an international incident, leading Secretary of State Antony Blinken to call off a planned trip to China only hours before he was set to depart.

China denies that the original balloon was being used for surveillance, saying it was a civilian research craft, and condemned the United States for shooting it down off the coast of South Carolina last Saturday.

With military and intelligence officials newly focused on airborne threats, at least two other flying objects were shot down over North America over the weekend.

U.S. Senate Majority Leader Chuck Schumer told U.S. broadcaster ABC that U.S. officials think the flying objects - the first of which was brought down over the sea ice near Deadhorse, Alaska, on Friday, and the second of which was destroyed over the Yukon on Saturday - were both balloons.

"They believe they were (balloons), yes, but much smaller than the first one," Schumer said.

The White House said only that the recently downed objects "did not closely resemble" the Chinese balloon, echoing Schumer's description of them as "much smaller."

Schumer said he was confident U.S. investigators scouring the ocean off South Carolina to recover debris and electronic gadgetry from the original balloon would get to the bottom of what it was being used for.

"We're going to probably be able to piece together this whole, whole surveillance balloon and know exactly what's going on," he said.

Canadian counterparts trying to piece together what was shot down over the Yukon may have their own challenges. The territory is a sparsely populated region in Canada's far northwest, which borders Alaska. It can be brutally cold in the winter, but temperatures are unusually mild for this time of year which could ease the recovery effort.

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In Whitehorse, the capital, the forecast is for a high of minus 2 Celsius (28 Fahrenheit) on Sunday.

Speaking to Fox News, House Foreign Affairs Committee Chairman Michael McCaul said the Chinese balloon was "an act of espionage in plain sight plain view of the American people," saying the balloon went over sensitive American nuclear sites.

"They want to get imagery, get intelligence on our military capability, particularly nuclear," McCaul said. "And they're building quite a nuclear stockpile themselves."

Surveillance fears may be making officials jumpy.

Twice in 24 hours, U.S. officials closed airspace - only to reopen it swiftly. On Sunday, the Federal Aviation Administration briefly closed space above Lake Michigan. On Saturday, the U.S. military scrambled fighter jets in Montana to investigate a radar anomaly there.

North American Aerospace Defense Command (NORAD) later said the pilots did not identify anything corresponding to the radar hits.

Republican lawmaker Mike Turner, who serves on the U.S. House Armed Services Committee, suggested that President Joe Biden's administration might be overcompensating for what he described as its previously lax monitoring of American airspace.

"They do appear somewhat trigger-happy," Turner told CNN on Sunday.

"I would prefer them to be trigger-happy than to be permissive."