Most Puerto Ricans have power restored after massive New Year's Eve blackout

• Energy company LUMA, which took over control of the U.S. territory's power transmission and distribution in 2021, said in a statement the exact cause of the New Year's Eve blackout remains under investigation.
• Early investigations pointed to a fault on an underground power line, the company reported.

The latest: As of LUMA's most recent update Wednesday morning, just over 85% of customers have had their service restored.

• The company reported Tuesday that power had also been restored to the Centro Médico and el Hospital Municipal de San Juan.
• LUMA initially predicted it would take one to two days to return power to every customer on the island.
• At the outage's peak, nearly 90% of 1.47 million LUMA clients were in the dark.

State of play: Puerto Rico's Gov. Pedro Pierluisi said Tuesday that President Biden and Energy Secretary Jennifer Granholm assured the island it would have federal assistance in "continuing and speeding up" the reconstruction of its electric system.

• In a separate Tuesday post, Pierluisi wrote that he is "demanding answers and solutions" from LUMA and Genera PR, another company that handles private electricity production on the island.
• Governor-elect Jenniffer González Colón, who is set to be sworn in Thursday, wrote in a Tuesday post that stabilizing the island's energy grid will be her top priority once she assumes office.

• "We can't keep relying on an energy system that fails our people," she wrote. "Today's blackout and the uncertainty around restoration continue to impact our economy and quality of life."

Catch up quick: The U.S. territory's energy was privatized after Hurricane Maria ravaged the grid in 2017, leaving hundreds of thousands in prolonged darkness.

• Operational control was transferred to LUMA, in hopes it could help remedy the damaged system. But the challenges have persisted.

Go deeper: Puerto Rico's grim outlook