NEW YORK (CBSNewYork) — LaGuardia Airport resumed normal full operations overnight after an electrical emergency at a Con Edison substation in Queens lit the night sky across much of New York City and spawned a flurry of social media reaction.

There were lots of wild ideas floating around about what the cause of the bright blue flash was. Some said it was a spaceship landing, others joked it was the biggest gender reveal party ever. It turned out to be much less exciting: An equipment malfunction at at Con Ed facility.

Watch: Gov. Andrew Cuomo Discusses Con Ed Explosion

The NYPD initially reported a transformer exploded at the utility company’s facility in Astoria shortly after 9 p.m. on Thursday, reports CBS’2 Natalie Duddridge. A follow-up statement from Con Edison called the failed equipment voltage monitoring gear within the substation.

Con Edison took Twitter Friday to say the incident caused “a sustained electrical arc flash & transmission disturbance.”

There were no injuries and a spokesperson told CBS2’s Reena Roy there were no lingering fumes or anything dangerous substances in the air.

“The equipment that malfunctioned is associated with voltage monitoring within the substation,” said ConEd in a statement. “There were no serious injuries, although one employee at the substation reported eye irritation associated with the arc flash.”

An electrical fault at the 138,000-volt Astoria east substation caused a flash, emitting a halo of light from the facility at 20th Avenue and 32nd Street.

“It was nuts. The entire sky went green. I though aliens were landing,” said Astoria resident David Brown. “You think nuclear war maybe, you think North Korea or something. You really don’t know what’s going on.:

Thousands of people posted cell phone video of the glowing blue hue that was magnified by last night’s cloud cover and could be seen from miles away.

Transformer explosion in New York City on Dec. 27, 2018 (credit: Hoboken Police Chief Ken Ferrante)

“All my power went off. I saw flashing blue light, ran to the other side of my house where my parents were sleeping, woke them up because I thought something horrible was happening,” said Astoria resident Spencer Pesce. “I thought it was aliens.”

But it wasn’t an invasion.

LaGuardia Airport had to run on backup generators, causing a ground stop and delaying flights from taking off for at least an hour, but was running again around 11 p.m.

The explosion also knocked out power out at Rikers Island, and some subway lines were disrupted including on the E, F, and R trains and the 7 line.

“We received numerous 911 calls, one that reported a plane crash,” said NYPD Deputy Inspector Osvaldo Nunez. “All the other calls were related to explosions.”

Police also said a few people voiced worries about what was, to them, clearly a potential alien invasion.

The fire department and Con Edison crews responded and restored all major transmission lines. Authorities said early this morning the system has been stabilized.

WATCH: Chopper 2’s Dan Rice Over the Scene in Queens 

“It was an explosion like fire, like a ball of fire,” one woman told CBS2. “One boom, and then boom boom boom boom boom!”

WATCH: CBS2’s Ali Bauman From LaGuardia Airport 

CBS2’s meteorologist John Marshal says the blue hue was magnified by the cloud cover.

“Process known as refraction, sometimes the elements in the clouds, or water droplets. So this explosion, even though it was white, and it was fiery, came back as a blue hue,” Marshal explained.

People immediately took to social media to post images of the sky across the city illuminated by an eerie blue-green light.

https://twitter.com/NYPDChiefofDept/status/1078489168924291073