For the first time in the 100 days since Hurricane Maria slammed Puerto Rico, the government finally knows how many people still don’t have power: about half.

The figure released Friday by the island’s governor and power utility company indicates that more than 1.5 million people on the island are still in the dark. Experts say some parts of the island are not expected to get power back until next spring.

“We understand how difficult it has been for the people for Puerto Rico who have been without power for so long,” said Ricardo Rosselló, the governor of Puerto Rico, as he announced a request for up to 1,500 more restoration workers from the mainland’s electric industry.

In its statement on Friday, the authorities said power restoration has been slow because of the sheer scale and complexity of the damage. Much of the island’s 2,400 miles of transmission lines, 30,000 miles of distribution lines and 342 substations were damaged in the storm, they said. Carlos D. Torres, the system’s restoration coordinator, said workers were finding “unexpected damage” in some areas even as they make repairs in others.