Elon Musk joked that the UAPs shot down over North America are alien 'friends of mine' as questions remain over their origins

• Elon Musk joked on Sunday about the latest UAP to be shot down over North America.
• "Just some of my [alien] friends of mine stopping by," the SpaceX CEO tweeted.

As officials continue searching for answers about the three unidentified flying objects which have been shot down over North America in recent days, Elon Musk has weighed in with a joke.

"Don't worry," the SpaceX CEO tweeted Sunday. "Just some of my [alien] friends of mine stopping by," he added, including emojis of an alien and a flying saucer.

Musk's quip came an hour before an American F-16 fighter jet shot down an object over Lake Huron, Michigan. The same object had been tracked from Montana, where it flew over sensitive military sites, the Pentagon said.

Like the two other downed objects, officials decided it was a risk to civilian aircraft due to the altitude at which it was flying, the statement said.

The Chinese spy balloon — which was shot down off the South Carolina coast on February 4 — was flying at a much higher altitude and couldn't be taken down earlier due to a risk of debris hitting civilians, Defence Secretary Lloyd J. Austin III said.

Earlier on Sunday, Musk tweeted: "Hopefully, one day we will be the aliens visiting other worlds."

The SpaceX CEO has made clear his plans to make humanity an interplanetary species. Last Thursday, Musk said it's "highly likely" humans will go to Mars within ten years, but added that he's "congenitally optimistic."

In addition to the object over Lake Huron, unidentified anomalous phenomena — the government's name for UFOs — were also shot down near Deadhorse, Alaska, and over Canada's Yukon territory, on Friday and Saturday respectively.

While officials were able to determine that the spy balloon came from China, they're not yet sure where the most recent three airborne objects are from. The Yukon object was described by Canadian authorities as "cylindrical," while an anonymous official told Reuters that the one over Lake Huron was "octagonal" and apparently had no payload like the Chinese spy balloon.

Efforts to figure out what the objects are and where they came from are ongoing, as officials recover wreckage.

General Glen VanHerck, the NORAD commander, said he hadn't ruled them out as being extra-terrestrial, per Reuters. However, there's no suggestion the devices came from another planet, The New York Times reported a senior official as saying.