A blackout has hit Puerto Rico, one of the territories in the United States, plunging nearly all of the island into darkness on New Year’s Eve.

The sweeping blackout began on Tuesday morning, affecting 13 per cent of the 1.4 million utility customers in the city.

The Luma Energy, which supplies power to the U.S. territory, said it was activating emergency operations to restore power and described the blackout as “system wide.”

“Preliminary findings point to a fault on an underground line,” it said on a social media post.

The energy company explained that it planned to restore power in phases and that “the entire process will take between 24-48 hours, conditions permitting.”

The director of the Puerto Rico Electric Power Authority, Josué Colón, said that he believed restoration would take several days.

Puerto Rico has faced a series of blackouts since 2017, when Hurricane Maria severely damaged the island, including its power grid.

The blackout appeared to be significantly bigger than more recent outages this summer.

In June, about 350,000 customers were left in blackout without power.