A giant plume of smoke colored by bright blue light exploded into the night sky on Thursday in Queens, causing people across New York City to gawk in awe before the authorities determined an electrical transformer was to blame.
The bizarre sight set off a frenzy on social media, where people reported power failures at La Guardia Airport. A spokesman for the Federal Aviation Administration said a ground stop was ordered there around 9:30 p.m. because of the power failure but was lifted after about 45 minutes; the airport then resumed its operations, he said.
After a stoppage because of the power failure, the Metropolitan Transportation Authority said in a tweet that No. 7 train service had resumed making all stops, but it warned of “extensive delays” in both directions.
Rikers Island prison complex, which houses about 10,000 inmates, lost power for about 25 minutes, according to a woman who answered the phone at the North Infirmary Command on the island.
By about 10:13 p.m., Chief Terence A. Monahan of the New York Police Department said on Twitter that there were no injuries as a result of the explosion. Around the same time, the New York Fire Department said there was “no fire.”
In a statement on Twitter, Con Edison said there had been “a brief electrical fire” at one of its substations in Astoria, “which involved some electrical transformers and caused a transmission dip in the area.” Police and fire officials said they continued to investigate the situation after having responded to the substation on the 1700 block of 31st Street. Mayor Bill de Blasio said the blue light was caused by an electrical surge there.
As of about 10:50 p.m., Con Edison’s outage map showed only about 50 power failures. On Twitter, officials apologized to dozens of alarmed customers, saying they “are aware of this situation.”
Bill San Antonio, 28, was waiting to board a flight to Dallas when the power went out at La Guardia. A blue light filled the sky outside the terminal windows.
“It was a weird shade of blue — a sort of unnatural, fluorescent shade of blue,” he said. Surrounded by other clueless passengers, he made his way through darkened hallways until he found his way outside.
“There’s been confusion pretty much from the start,” Mr. San Antonio said, adding that the power seemed to be out inside the airport for about 20 minutes. After that, he returned to the security line — but then he got a text message saying his flight had been canceled.
Residents milling about the blocks surrounding the substation said they heard a boom and saw shades of blue and green filling the night sky.
“We thought it was a U.F.O.,” said Yiota Androtsokis, who has lived in the area for nine years and said nothing like this had happened before.
Lights flickered on and off, she said. “It was making a weird noise,” she added, a sound she and other neighbors described as a loud, continuous hum. Ms. Androtsokis said it was so loud she heard it through closed windows; even after it ceased, she could still hear it in her ears.
The lights were so bright, she said, that in some places an otherwise dark night was as bright as day.
Ms. Androtsokis was not the only New Yorker worried about an alien invasion. In the earliest moments, hundreds of Twitter users from across the city posted videos of the eerie lights, causing many on social media to posit that theory.
The authorities, though, had none of it, assuring the public that no alien landing had occurred.
Closer to the power plant, Peter Dipietrantonio said he and his girlfriend heard a bang and then saw a “green aura” fill his window. Moments later, he said he saw people rushing away on the street. “Once we saw people running, we decided to get out,” he said. His girlfriend, Dana Jefferson, stood on the street, carrying the duffel bag she had quickly packed. “She was ready to go,” he said.
Outside the power plant, the police had cordoned off a few blocks as helicopters hovered above.
Andrew R. Chow, Daniel Victor and Margaret Kramer contributed reporting.