More than 1.3 million people were plunged into darkness early Tuesday. Failure of an underground power line is believed to be the cause and repairs could take up to two days.

After some areas of Puerto Rico welcomed the New Year in the dark amid a massive failure to the island’s power grid, service has been restored to nearly all impacted customers.

Power outages are a frustratingly frequent occurrence for many Puerto Ricans. A string of blackouts during the summer prompted protests and a state of emergency.