The U.S. military downed an unidentified object that was flying in territorial waters over Alaska on Friday, National Security Council spokesperson John Kirby said during a press briefing.

“I can confirm that the Department of Defense was tracking a high altitude object over Alaska airspace in the last 24 hours out," Kirby said.

He said the object, which was “roughly the size of a small car” and flying at an altitude of 40,000 feet, "posed a reasonable threat to the safety of civilian flight." Kirby had no details about the origin of the object.

"Out of an abundance of caution and the recommendation of the Pentagon, President Biden ordered the military to down the object," he said. Kirby later said Biden gave the orders on Friday morning, just one day after the flying object was discovered.

The military shot the object down and it "came in inside our territorial waters," he said.

A U.S. official told the New York Times there were "no affirmative indications of military threat" to people on the ground from the object. Officials could not confirm if there was surveillance equipment on the object.

The incident comes less than a week after the U.S. military shot down a suspected Chinese spy balloon off the Carolina coast last week. The Pentagon first became aware of the balloon in late January, when it entered U.S. airspace in Alaska. The balloon was part of a larger surveillance program run by the People's Liberation Army, according to the Washington Post.

The program has collected information on military assets in a number of countries, including Japan, India, Vietnam, Taiwan and the Philippines, U.S. officials reportedly told the Washington Post.

One official called the scheme a "massive effort" by China using an "unbelievably old technology" that it joined with "modern communications and observation capabilities" in an effort to gather intelligence on other countries' militaries.

The program has carried out dozens of missions since 2018, according to the report. The balloons, which fly between 60,000 and 80,000 feet or higher, supplement China's long-range surveillance efforts that are typically conducted via military satellite array.

Four balloons were seen above Hawaii, Florida, Texas and Guam in recent years, according to the report. While several former high-ranking Trump officials pushed back on the Biden administration's recent claim that at least three Chinese spy balloons flew over the United States during the previous administration, officials have since said the balloons were only recently identified as Chinese surveillance airships.