Billings, Montana - The Pentagon is tracking a Chinese spy balloon that has been flying over the US for at least a couple of days, officials announced Thursday.

The Pentagon said that the trajectory of the balloon, last spotted floating over Montana, was being closely followed and confirmed that the device was still within US territory.

It had crossed Canadian airspace on its way, and authorities north of the border confirmed they were also aware of the balloon.

The Department of Defense said it considered shooting it down, but decided against it, due to the danger of falling debris.

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Authorities are certain the balloon comes from China.

Similar incidents have happened in the past, however this time the device has remained over US territory longer than usual. According to the Pentagon, the balloon poses no danger to aircraft due to its high altitude. The US is in contact with China about the incident.

On Friday, the Guardian cited a spokesperson for the Chinese ministry of foreign affairs, who said the incident was under investigation and added: "I would like to emphasize that until the facts are clarified, speculation and hype will not be helpful to the proper resolution of the issue."

The US stores silo-based nuclear missiles in Montana, but there's no indication the balloon was able to gather any kind of intelligence that's not already available via satellite surveillance.