(Reuters) – A transformer explosion at an electric power substation in the New York City borough of Queens lit up the night sky with a bright blue light on Thursday, mystifying some residents, but officials said no one was injured in the incident.

“There was a boom and a bang and a flash of light,” said Jim Long, a spokesman for Fire Department New York.

“It’s all under control but we’re still getting calls from residents wondering what happened,” he said early on Friday.

The blue flashes that briefly lit up the night sky in the Astoria area of Queens, New York, shortly after 9 p.m. (0200 GMT) were caused by a power surge and electrical “arching” and sparked a transformer explosion and a small fire, said Con Edison spokesman Bob McGee.

There were no injuries, he said.

Social media lit up with videos and photos of the bright light in the night sky over New York City. The chatter continued into Friday morning.

“Why is the sky lit up bright blue in Queens New York City right now? Is it fireworks?” Louis Santoro, a New York City resident, wrote on Twitter.

One resident, Joe Calderone, told the New York Post: “Damn, I thought a UFO hit Con Ed.”

Con Edison’s McGee reassured residents after internet speculation that aliens or the villain Thanos from the recent Avengers’ movie “Infinity War” had invaded.

“No, it wasn’t space aliens,” he said.

“All power has been restored to normal. “But the videos online of the blue lights in the sky are still flying all over the internet,” McGee said.

The fire caused scattered outages, stalled some city trains and briefly blacked out LaGuardia Airport, which is located in Queens, because of a transmission dip, he said.

It also caused some flight cancellations and delays but all power and services were restored before midnight, McGee said.

New York City Mayor Bill de Blasio said in a message on Twitter that Con Edison was evaluating the extent of power outages in the area.

He said that travelers could expect delays through early Friday.

The cause of the incident was being investigated.