SAN JUAN, Puerto Rico — Cheers erupted as lights slowly began to flicker back on across Puerto Rico overnight as the U.S. territory struggled to emerge from an island-wide blackout following a fire at a power plant that caused the aging utility grid to fail.

About 75 percent of 1.5 million homes and businesses served by the power utility had electricity restored by Friday morning, with cries of, “The lights are back on!” echoing through some neighborhoods.

“We’ve surpassed our expectations,” Gov. Alejandro Garcia Padilla said. “We’re working hard to restore power to our other customers … I understand the annoyance of being without electricity.”

He anticipated that the majority of Puerto Ricans will likely have power by Saturday, more than 72 hours after the island-wide outage.

The lights went out briefly during Friday’s press conference at the island’s emergency operations center, provoking a laugh from government officials addressing reporters. Garcia said temporary power outages would still occur in upcoming days given the growing demand for electricity as more and more customers became reconnected.

The blackout hit the entire island of 3.5 million people early Wednesday afternoon and prompted Garcia to activate the National Guard and declare a state of emergency. Public schools remained closed on Friday, and heavy storms that hit the island Thursday afternoon knocked out power to some areas where electricity had been restored. Meanwhile, some 205,000 people remained without water.

While those with power celebrated a return to normalcy, others lamented having spent another night in darkness with no air conditioning in the tropical heat. Most Puerto Ricans don’t have generators, and many once again dragged mattresses out to balconies and porches to spend the night outside.