A massive spy balloon believed to be from China was seen above Montana and is being tracked as it flies across the continental United States, with President Joe Biden for now deciding against "military options" because of the risk to civilians, U.S. officials said on Thursday.
Still, officials insisted, they continue to closely monitor the vessel as they have since it entered the country -- while voicing their concern to the Chinese.
"The United States government has detected and is tracking a high-altitude surveillance balloon that is flying over the continental United States right now," Brig. Gen. Pat Ryder said in a statement on Thursday.
"NORAD [North American Aerospace Defense Command] continues to track and monitor it closely," Ryder said. NORAD later said in a statement that its commander, Gen. Glen VanHerck, "assesses the balloon does not present a military or physical threat to people on the ground at this time. The balloon is currently traveling at altitude well above commercial air traffic."
Canada's Department of National Defence and the Canadian Armed Forces are working with NORAD and "other partners" to assess the situation, the agency said in a statement, adding that Canada is "taking steps to ensure the security of its airspace, including the monitoring of a potential second incident."
The high-altitude reconnaissance balloon was not the first such craft to pass over the U.S. in this way, a senior defense official said in a briefing.
A separate senior official told ABC News the balloon is the size of three buses and complete with a technology bay, which the defense official said they "wouldn't characterize" as "revolutionary."
The defense official said they "are confident" the balloon was sent by China.
"Instances of this activity have been observed over the past several years, including prior to this administration," the official said, noting that "it's happened a handful of other times over the past few years ... It is appearing to hang out for a longer period of time this time around."
One outside expert predicted the balloon could be essentially scientific and set off course, though other sources said it appeared to be "purposeful."
Retired Col. Steve Ganyard, an ABC News contributor, said the balloon looked to be a standard research vessel -- which would mean it was unpowered and drifted with the jet stream.
A senior U.S. official, however, told ABC that the military balloon was specially designed, with a purposeful path. They believe the balloon can take high-resolution pictures and is flying along areas where there are missiles and bases.
Echoing that, the defense official told reporters: "I'm not trying to be a wise guy, but the goal was surveillance and clearly they're trying to fly this balloon over sensitive sites ... to collect information."