New York - A relay protection system that should have isolated a faulty distribution cable but didn’t led to the loss of power that darkened Manhattan for several hours.

Con Edison says a preliminary review of Saturday’s blackout shows that the relay system at a West 65th Street substation should have kept the problem from spreading.

Instead, the electrical fault was isolated at a transmission substation at West 49th Street.

The blackout resulting from the system’s failure affected thousands for about five hours along a 40-block stretch that included some of Manhattan’s busiest areas like Times Square and Rockefeller Center.

It also raised criticism of New York City Mayor Bill de Blasio because he was in Iowa for his presidential campaign at the time.