SAN JUAN, Puerto Rico (AP) -- A major blackout hit Puerto Rico's most populated region on Wednesday just as the government announced it had met its goal of 50 percent power generation nearly two months after Hurricane Maria struck as a Category 4 storm.
The Puerto Rico Electric Power Authority (PREPA) said it dispatched crews to investigate why a key 230 kV transmission line that connects the island's northern and southern regions had failed for the second time in a week.
The blackout affected the capital of San Juan and nearby cities and towns along the U.S. territory's north coast, provoking a groan from people who were celebrating the return of electricity in recent weeks by restocking refrigerators and charging phones and computers.
A previous blackout involving the same line occurred on Nov. 8.
On social media, some Puerto Ricans wondered whether the blackout was caused by the government's rush to meet its goals to restore power. Puerto Rico Gov. Ricardo Rossello has pledged 95 percent power generation by Dec. 15, while the U.S. Army Corps of Engineers has said it expects 75 percent power generation by the end of January.
Susan Tierney, a senior advisor for Denver-based consulting company Analysis Group who testified last month before a U.S. Senate committee on efforts to restore power, said blackouts are likely to occur if a power company is having problems matching supply and demand.
"Something has to give," she said in a phone interview, adding that she is surprised at how slowly power is being restored across the U.S. territory. "It's extraordinary to have an outage that has extended this deeply and for so long after an event."
More than 130,000 people have fled the island since the hurricane, with many who are able seeking jobs and shelter on the U.S. mainland.
Prior to Wednesday's blackout, the power company said 21 municipalities still had no power at all, and portions of Puerto Rico's 57 other municipalities had seen electricity restored.
The island's power outage was the worst in U.S. history.