A failure of the substation's relay protection system has caused the Manhattan blackout in New York City, the Con Edison energy company said in a statement on Monday.

Power has been restored five hours after a large outage affecting over 44,000 people hit much of Manhattan's midtown and part of the Upper West Side in New York City on Saturday evening.

There have been no reports of injuries or fatalities, said a spokesperson for the local emergency department.

New York City Mayor Bill de Blasio said on Twitter that he has "directed City agencies to investigate this evening’s blackout," in order to prevent another widespread outage like this. 

The CEO of Con Edison, a power service company said that the power is being restored on Manhattan's Upper West Side, and the goal is "to have all power restored by midnight."

New York City Mayor Bill de Blasio said on Twitter that the power outage was caused by a “manhole fire,” adding that the “disruption is significant.”

The electrical failure has dimmed Times Square and the Rockefeller Center and impacted subway stations. The New York City Office of Emergency Management said it had activated its emergency operations center.

(Cover: People are evacuated outside Row NYC hotel, as a blackout affects buildings and traffic during widespread power outages in the Manhattan borough of New York, U.S., July 13, 2019. /Reuters Photo)