The near-Earth object was thought to pose a slight risk of impacting Earth in 2068, but now radar observations have ruled that out.

After its discovery in 2004, asteroid 99942 Apophis had been identified as one of the most hazardous asteroids that could impact Earth.

A spectacular display of lights that streamed across the night sky over the US Pacific Northwest was probably debris from a SpaceX mission re-entering the atmosphere, the National Weather Service (NWS) said.

"While we await further confirmation on the details, here's the unofficial information we have so far. The widely reported bright objects in the sky were the debris from a Falcon 9 rocket 2nd stage," NWS Seattle tweeted.

Videos posted on social media showed a thick cluster of glowing dots with blazing trails of light moving slowly across the sky before fizzling out, with users speculating the phenomenon might be a meteor shower or even, jokingly, an alien invasion.

Local media reported multiple sightings just after 9 pm local time, with videos posted online from Washington state and Oregon.

NWS Seattle said the sight was more likely to be caused by space debris rather than a meteor or similar object because the latter would be moving far faster, a conclusion backed up by several meteorologists quoted by local media.

Jonathan McDowell from Harvard's Center for Astrophysics also pointed to the Falcon 9 rocket stage as the source of the firework-like display.