(CNN) Power was starting to come back to parts of New York on a warm Saturday night as ConEdison restored electrical service on the west side of Manhattan after widespread power outages canceled shows and sent tens of thousands of people onto darkened streets, officials said.

There were 16,000 customers without power in Midtown Manhattan and the Upper West Side, utility company ConEdison said. At its peak, the number was about 72,000, it said.

The company estimated most customers will have power restored by midnight.

As he spoke to reporters, the lights came on in buildings behind him and the crowd cheered loudly.

Just before the lights and air conditioners began to come back on, Gov. Andrew Cuomo said the numbers of customers without power had soared from 20,000 right after the blackout started because transformers kept tripping.

The power outage sent people into intersections to direct traffic, brought at least one troupe from a canceled Broadway show out to perform for fans on a crowded sidewalk, and prompted giddy tourists and locals to point smart phones at darkened neon signs in Times Square and other places.

It also temporarily trapped people on trains and in elevators.

Mayor Bill de Blasio, who was returning to the city after a presidential campaign stop in Iowa, said it appears the outage was the result of a mechanical problem in the electrical grid.

"This appears to be something that just went wrong in the way that they transmit power from one part of the city to another," he told CNN. "It sounds like it is addressable in a reasonable amount of time."

ConEd CEO John McAvoy said the company is working to understand the cause of the outage and needs to do a full engineering analysis.

Photos: Parts of Manhattan in the dark after power outage Seen from the air, a large section of Manhattan's Upper West Side and Midtown neighborhoods stand coated in darkness on Saturday, July 13. Hide Caption 1 of 18 Photos: Parts of Manhattan in the dark after power outage Times Square's billboards are black as people fill the street. Hide Caption 2 of 18 Photos: Parts of Manhattan in the dark after power outage People use their phones as flashlights. Hide Caption 3 of 18 Photos: Parts of Manhattan in the dark after power outage Pedestrians looks at their cellphones in midtown Manhattan. Hide Caption 4 of 18 Photos: Parts of Manhattan in the dark after power outage Radio City Music Hall is dark during the blackout. Hide Caption 5 of 18 Photos: Parts of Manhattan in the dark after power outage An entrance to the C and E trains at the 50th Street Subway Station is dimly lit. Hide Caption 6 of 18 Photos: Parts of Manhattan in the dark after power outage People sit inside a bar during the power outage. Hide Caption 7 of 18 Photos: Parts of Manhattan in the dark after power outage Dark buildings along a dark street are seen near the Times Square area. Hide Caption 8 of 18 Photos: Parts of Manhattan in the dark after power outage Con Edison workers stand around a barricaded transformer cover. Hide Caption 9 of 18 Photos: Parts of Manhattan in the dark after power outage People are evacuated outside Row NYC hotel. Hide Caption 10 of 18 Photos: Parts of Manhattan in the dark after power outage A convenience shop is closed. Hide Caption 11 of 18 Photos: Parts of Manhattan in the dark after power outage A man directs traffic on 8th Avenue and West 58th Street. Hide Caption 12 of 18 Photos: Parts of Manhattan in the dark after power outage The Upper West Side of Manhattan is in the dark. The city's fire department was responding to numerous transformer fires, the first of which occurred in Manhattan on West 64th Street and West End Avenue, officials said. Hide Caption 13 of 18 Photos: Parts of Manhattan in the dark after power outage People walk along a dark street near Times Square. Hide Caption 14 of 18 Photos: Parts of Manhattan in the dark after power outage A police officer directs traffic in Times Square. Hide Caption 15 of 18 Photos: Parts of Manhattan in the dark after power outage A view of the Hell's Kitchen neighborhood shows buildings in darkness. Hide Caption 16 of 18 Photos: Parts of Manhattan in the dark after power outage A train sits out of service at Penn Station. Hide Caption 17 of 18 Photos: Parts of Manhattan in the dark after power outage Buildings near Columbus Circle are dark. Hide Caption 18 of 18

The city's fire department responded to numerous transformer fires, the first of which occurred in Manhattan on West 64th Street and West End Avenue, officials said.

Several Broadway and off-Broadway shows said they were canceling performances, according to tweets aggregated by The Broadway League

Firefighters also responded to people trapped in elevators and subway cars, and they are operating all over Manhattan's West Side from streets in the 40s to the 60s, according to an FDNY spokesman.

Some of the cast from "Come From Away" came outside as people awaited news of whether the show would be call off and they sang a number.

The outage was having a widespread effect on the New York subway system, which was experiencing power outages in its stations, the agency managing the trains said.

"Subway service remains significantly disrupted across the system, although there is limited service on the 1/2/3 and 4/5/6 lines," the Metropolitan Transportation Authority tweeted.

Update: Con Edison continues to work to resolve the power outage in Manhattan.



Subway service remains significantly disrupted across the system, although there is limited service on the 1/2/3 and 4/5/6 lines.



Local bus routes are your best bet for travel within Manhattan. (1/2) pic.twitter.com/RV8EiFLYZx — NYCT Subway (@NYCTSubway) July 14, 2019

The MTA advised people to stay away from underground stations.

The outages were affecting "multiple lines," the MTA said, so trains were using a "local track."

The MTA told people to consider taking the bus.

The lack of power was a major issue on the streets and in buildings, too.

A CNN producer on the Upper West Side said he was at a movie when the theater went dark at about 7 p.m. He went outside and saw traffic and street lights were out. Traffic was jamming up in intersections but it wasn't gridlocked, he said.

Twitter user Sahid Abraham posted a photo from Times Square that showed some of the famous electronic billboards dark.

Times Square is down, i repeat, Times Square is down. This is not a drill!! #Blackout #NYC pic.twitter.com/8IUfER7ozl — Sahid Abraham (@Sahid0) July 13, 2019

Another user posted a photo showing a man at 66th Street and Broadway directing traffic.

No cops directing traffic at 66th Street and Broadway. Up to the #fruitstandguy to direct traffic because of the #blackout in nyc pic.twitter.com/jQpCC8TgMI — wilkssc (@wilkssc) July 13, 2019

A woman jumped in to help at a nearby intersection.

Lake Escobosa, 23, a dancer living in Brooklyn, spent nearly an hour directing traffic, marshaling cars, ambulances and pedestrians through a busy, three-way intersection near New York's Lincoln Center on Manhattan's Upper West Side.

She said she learned her traffic directing skills from her father, a former police officer who walked the beat in Coney Island.

"I know how tricky it is when it comes to that intersection and I just saw in my mind car accidents people getting hit, people screaming," she said. "So I felt like I should have just tried."

On Columbus Avenue, outside Fordham University's campus, the scope of the outage was becoming more apparent as daylight waned. There were very few lights in building windows and brightly lit food carts were some of the few sources of light beyond vehicle headlights.

There were no reports of injuries.

The outages come 42 years to the day of an extensive blackout that affected much of the city.