"I know there have been questions and concerns about this, but there is no, again no indication of aliens or extraterrestrial activity with these recent takedowns," White House press secretary Karine Jean-Pierre said.

The White House's denial marks an about face for the U.S. government. On Sunday, a U.S. Air Force general said he would not rule out aliens or any other explanation yet, deferring to U.S. intelligence experts.

The general's comments came during a Pentagon briefing on Sunday after a U.S. F-16 fighter jet shot down an octagonal-shaped object over Lake Huron on the U.S.-Canada border. It was the third shootdown of an unidentified object following the Feb. 4 downing of a Chinese balloon off the South Carolina coast that put North American air defenses on high alert.

U.S. officials said that balloon was being used for surveillance.

The objects' origins has been the subject of intense interest and speculation in the United States. Just under half of Americans believe UFOs exist and have visited the earth, according to a 2020 IPSOS poll.

Multiple White House officials ruled out the possibility that the objects came from extraterrestrials on Monday.

"I don't think the American people need to worry about aliens with respect to these crafts, period," White House spokesperson John Kirby said during a White House briefing with reporters on Monday.

The incidents come as the Pentagon has undertaken a new push in recent years to investigate military sightings of UFOs - rebranded in official government parlance as "unidentified aerial phenomena," or UAPs.

The government's effort to investigate anomalous, unidentified objects - whether they are in space, the skies or even underwater - has led to hundreds of documented reports that are being investigated, senior military leaders have said.

A U.S. government report in June of 2021 that did not rule out possible extraterrestrial origin for 144 "unidentified aerial phenomenon."

That report marked a turning point after the military spent decades deflecting, debunking and discrediting observations of unidentified flying objects and "flying saucers" dating back to the 1940s.