The outage, which stretched 30 blocks from Times Square to the Upper West Side, left around 73,000 customers without power Saturday night for about four hours.
Electricity provider Con Edison said power was gradually being restored across the city. The utility did not immediately respond to phone messages, and it was unclear when they expected power to return.
More than 70-thousand people lost power at the peak.
The city's subway system had earlier said it was working with the Con Edison and that the outage was affecting Midtown and the Upper West Side.
When you're talking about a city like NY with a significant piece of the city, basically suffering a blackout, that could be a very chaotic situation.
The New York Fire Department said it was tackling a fire in an electrical transformer in Manhattan, the most densely populated of the city's five boroughs.
The blackout also affected a number of Broadway shows, with some theaters delaying their productions and halting admission, according to the Broadway League.
The outage extended from Fifth Avenue west to the Hudson River, and from the West 40s north to 72nd Street, authorities said.
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She said that the young royal won't be "paraded" on the tour as Prince Harry "doesn't want him to grow up with the burden he did". Only two photographs were released from that day, a family portrait and a sweet capture of newbie parents and their son.
The outage was having a widespread effect on the NY subway system, which was experiencing power outages in its stations, the agency managing the trains said.
ConEd Chief Executive Officer John McAvoy told reporters late Saturday that the company would investigate the root cause of the event and "restore the system to a fully normal condition once we understand what exactly occurred".
"We think the grid is sound", Cawley said Sunday, adding, "If there are lessons we can apply, we will".
When a massive blackout plunged much of Manhattan into darkness on Saturday evening, a choir and the casts of Broadway musicals entertained tourists with impromptu performances in the street. Meanwhile in the streets, some New Yorkers stepped up to help direct traffic at busy intersections where the traffic lights had gone out.
The current population of New York City is estimated at 8.5 million.
"I'm going to get more information in the next hour or so, and we'll adjust my schedule accordingly depending on what I hear", said de Blasio. "Definite causes will take some time" to figure out, he said.