A massive outage has wiped out power to Puerto Rico's capital San Juan.
The problem is with a failure on a main north-south transmission line, said Fernando Padilla, an official with the Puerto Rico Electric Power Authority, known as PREPA.
"It was a mechanical issue on the line, could have happened at any line," he said. "It's being patrolled and repaired by PREPA."
Power went out about 11:30 a.m. local time (10:30 a.m. ET).
Homes and businesses that had been on grid power had to restart generators if they had them.
Power generation plummeted from over 40% of capacity to 18% on Thursday, PREPA said.
Much of Puerto Rico has been without power since Hurricane Maria smashed the island on September 20.