A sold-out Jennifer Lopez concert came to a halt Saturday night in New York City as a massive power outage left more than 70,000 Manhattan customers in the dark.

Between Midtown Manhattan and the borough's Upper West Side -- an area that includes Broadway theaters -- dozens of other shows and plays also were forced to cancel and evacuate their buildings.

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Fox News correspondent Bryan Llenas, who was celebrating his birthday by attending Lopez's concert at Madison Square Garden, described his experience.

"We were about three songs in, the party was just getting started," he said, "and at about 9:25 the floodlights essentially came on, the power went out, and an announcement went out over the intercom, the speaker, saying that this was the building engineer and that as a precaution we need everybody to evacuate the building."

The power outage caused the so-called "World's Most Famous Arena" to be evacuated, with the estimated 19,000 audience members walking down service escalators to exit the building.

Lopez, who was performing for the second night in New York as part of her "It's My Party" tour tweeted: "Devastated and heartbroken that I can't perform for all of you tonight. We will make this up to you. I promise! I love you!!"

Dozens of theatergoers also lamented their show cancellations on social media.

The Saturday night showing of "Harry Potter and the Cursed Child" was canceled at the midway point.

One Twitter user said, "They just canceled [the] second part of Harry Potter on Broadway due to power issues-- tickets will be refunded...."

Others joked about the cancellation, "Harry Potter and the Cursed Electrical Grid."

Another Twitter user complained that she "came all the way from Philadelphia" to see the comedian Dave Chappelle perform standup on Broadway "but thanks to the #blackout show was canceled."

Performers of shows such as "Hadestown" and "Hamilton" took their shows outside and began performing in the streets of New York in an attempt to appease the disappointed masses.

But for one Broadway play, the show went on as the theater hosting the Tony-nominated show "Burn This," continued despite the power outage.

Fox News foreign desk director Greg Headen was settling in for a movie at an AMC theater on the Upper West Side when the power went out and staff members called for everyone to evacuate.

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"The movie hadn't started yet. Everything went black. AC went off. Everything just shut down and complete pitch dark," Headen said. "We were on the lower theatre which is actually underground and it was strange."