SpaceX’s first launch on the West Coast left the California skies glowing with a spectacular trail of light, forcing the Los Angeles mayor to inform residents they were not witnessing an alien invasion.

The SpaceX Falcon 9 rocket launched Sunday, to deploy an Argentinian satellite before successfully returning to land at the Vandenberg Air Force Base northwest of L.A.

While the rocket’s launch and subsequent return to Earth lasted just 15 minutes, it traced a bright luminescent trail across the sky that some people captured in pictures and video.

Social media users from as far away as Phoenix, Ariz. -- more than 850 kilometres form the launch site -- reported seeing the strange lights in the night sky.

In advance of the rocket launch, U.S. Air Force warned Californians that they might see multiple engine burns in the sky and hear one or more sonic booms on the rocket’s return to Earth.

SpaceX CEO Elon Musk also warned that the launch wouldn’t be “subtle,” but the rocket still caused a spike of Californians turning to Google for information about UFOs.

Los Angeles Mayor Eric Garcetti worked to defuse the speculation, tweeting that the bright, glowing light in the sky was in fact the Falcon 9 and “definitely not aliens.”

With files from Storyful and The Associated Press