Heightened awareness of potential airborne threats could account for the uptick in objects identified as the military downed a fourth mysterious flying object 15 nautical miles from Michigan coastline Sunday, North American Aerospace Defense Command (NORAD) leader Gen. Glen VanHerck said.

At the order of President Joe Biden, a U.S. F-16 fighter jet shot down the object over Lake Huron, near Michigan, at 2:42 p.m. Sunday, Pentagon spokesperson Brig. Gen. Pat Ryder said in a statement. While state and private entities operate in low-altitude airspace, the object downed over Michigan was unknown and did not respond to attempts to communicate and deconflict, officials explained Sunday evening.

The object downed Sunday was traveling at an altitude of 20,000 feet, significantly lower than the objects downed over Alaska and Canada the past two days, and could therefore pose a threat to commercial air traffic.

“Based on its flight path and data we can reasonably connect this object to the radar signal picked up over Montana, which flew in proximity to sensitive DOD sites,” Ryder said, noting that shooting it down over Lake Huron minimized the chance of harm to civilians. “We did not assess it to be a kinetic military threat to anything on the ground, but assess it was a safety flight hazard and a threat due to its potential surveillance capabilities.” (RELATED: Past Chinese Spy Balloons Were Classified As UFOs, Officials Say)

The Department of Defense (DOD) is on “heightened alert,” which could account for the sudden pace with which NORAD, responsible for air defense and early warning throughout North America, has picked up on strange airborne objects, VanHerck said. U.S. jets shot down two additional objects Friday and Saturday.

The command lowered the threshold on warning filters to capture signals from lower altitude, lower speed objects, he explained.

In recent years, NORAD has been able to adjust how it tracks and detects foreign airborne objects “and have better domain awareness” following an August intelligence report describing a significant uptick in unidentified aerial phenomena sightings, according to VanHerck.

“As far as these objects at this time I’m unaware to say,” VanHerck said when asked if NORAD was currently tracking additional objects. “It’s certainly possible.”

DOD has not been able to assess the origin or function of the last three objects downed over U.S. and Canadian airspace, homeland defense assistant secretary Melissa Dalton said Sunday.

2/ As long as these things keep traversing the US and Canada, I’ll continue to ask for Congress to get a full briefing based on our exploitation of the wreckage.

— Rep. Elissa Slotkin (@RepSlotkin) February 12, 2023

The object Sunday was octagonal and did not appear to carry a payload, a congressional aide told The Wall Street Journal.

On Saturday evening, the Department of Defense (DOD) imposed a temporary flight restriction over Montana to investigate a possible fourth object flying over Montana but could not make a positive identification, according to a statement.

However, Sunday afternoon the Federal Aviation Administration closed and reopened airspace over Lake Michigan as defense officials recapture the radar signal, CNN reported. Flight trackers showed U.S. Air Force and Coast Guard aircraft in the area.

Michigan members of Congress, including Republican Rep. Jack Bergman and Democratic Rep. Elissa Slotkin, first said DOD had informed them of the object’s demise in social media statements.