Power is back on in the Back Bay after a manhole fire partially knocked out service for roughly 30 NStar customers Sunday evening, according to NStar spokesman Mike Durand.

The fire, which spewed from a manhole near 461 Beacon St. around 8:45 p.m., was caused by a failing underground cable, Durand said. Crews were able to repair damaged equipment and the cable overnight and replace “fuse-type devices,” restoring full power to the half-dozen buildings affected, which were near Massachusetts Avenue and Beacon Street, he said.

It was the second power outage of the day in Back Bay on Sunday.

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At about 3:15 a.m., a cable that connected a transformer to the electrical grid at the Scotia Street substation — the same facility that was at the center of the March 2012 outage — malfunctioned and cut power to about 12,000 customers between the Charles River and Columbus Avenue, and between Copley Square and the Fenway neighborhood, Durand said in a previous interview.

Durand said around 8,000 of the affected customers had power back by about 9 a.m. Sunday and that after 10 a.m. only a handful of customers remained without electricity. By noon, power was restored to all customers.