BAYAMÓN, Puerto Rico — Power was restored to nearly all electrical customers across Puerto Rico on Wednesday after a sweeping blackout plunged the U.S. territory into darkness on New Year’s Eve.

By Wednesday afternoon, power was back up for 98% of Puerto Rico’s 1.47 million utility customers, said Luma Energy, the private company overseeing transmission and distribution of power in the archipelago. Lights returned to households as well as to Puerto Rico’s hospitals, water plants and sewage facilities after the massive outage that exposed the persistent electricity problems plaguing the island.

Still, the company warned that customers could still see temporary outages in the coming days. It said full restoration across the island could take up to two days.

“Given the fragile nature of the grid, we will need to manage available generation to customer demand, which will likely require rotating temporary outages,” Juan Saca, president of Luma Energy, said in a statement.

The lights went off in Puerto Rico at 5:30 a.m. on Tuesday, darkening almost the entire archipelago as people prepared to ring in the New Year. Authorities are still investigating the cause of the outage, but Luma Energy said a preliminary review pointed to a failure in an underground electric line in the south of the territory.

Governor-elect Jenniffer González Colón, who is set to take office on Thursday, warned that customers might experience interruptions in the coming days, with power plants not yet operating at maximum capacity.

“These days, I urge you to be moderate with your energy consumption to help reduce load shifting, so that more people can have access to electricity and the system can start up without any major setbacks,” González Colón said on social media platform X.

On the campaign trail, González Colón had promised to appoint an “energy czar” to oversee the operation of the power grid, which has long been fragile and faulty due to years of neglect.

The island’s power grid was ravaged in September 2017 by Hurricane Maria, a Category 4 storm.

Unreliable electricity remains frustratingly common, hindering daily life for Puerto Ricans. In June, over 340,000 customers were left without electricity as people reeled from soaring temperatures. At the peak of Hurricane Ernesto, in August, over half of all utility customers lost power. Tens of thousands of people remained without electricity a week after the storm.

The New Year’s Eve outage came as clients brace for a hike in electricity rates. Last month, Puerto Rico’s Energy Bureau approved an increase of 2.2 cents per kilowatt hour for residential customers from January through March, causing electric bills for the average household to jump by nearly $20, the Energy Bureau says.