A power outage struck across most of Puerto Rico early Tuesday as the U.S. territory prepared for New Year’s celebrations, leaving more than 1.3 million customers in the dark. Officials said it could take up to two days to restore power. The outage occurred at dawn, plunging the island into an eerie silence as electrical appliances and air conditioning shut down before those who could afford generators turned them on.

According to Luma Energy, a private company that oversees electricity transmission and distribution, nearly 90% of the 1.47 million customers across Puerto Rico remained in the dark. Luma said in a statement that the outage appeared to have been caused by the failure of an underground power line and said power would be restored “in the fastest and safest possible manner.” The blackout fueled simmering anger against Luma and Genera PR, which oversees electricity production in Puerto Rico, as more people call for their ouster.

Gov.-elect Jenniffer González Colón, who is scheduled to be sworn in on Jan. 2, has called for the creation of an “energy czar” to review possible contract violations by Luma while another operator is found. Meanwhile, Governor Pedro Pierluisi said he was in contact with Luma and Genera PR, adding on X that “we demand answers and solutions.”

While power outages are rare in Puerto Rico, the island struggles with chronic power outages stemming from a crumbling power grid that was leveled in September 2017 by Hurricane Maria, a Category 4 storm. However, the system was already in decline after years of blackout maintenance and investment.

Most recently, crews began making permanent repairs to Puerto Rico’s power grid following Hurricane Maria. To stabilize the grid, the island continues to rely on generators provided by the U.S. Federal Emergency Management Agency. In November, Puerto Rico’s government asked U.S. officials for permission to continue using more than a dozen portable generators for two more years.

Meanwhile, Puerto Rico’s Electricity Authority, the island’s largest government agency, is struggling to restructure more than $9 billion in debt.