A blackout hit northern Puerto Rico late Sunday after an explosion set off a big fire at a main power substation in the U.S. territory.
Officials with the island's Electric Power Authority said several municipalities were without power, including parts of the capital of San Juan.
It was not immediately known what caused the fire, although officials said the explosion knocked two other substations offline and caused a total loss of 400 megawatts worth of generation.
"We are trying to restore that as quickly as possible," the company said.
Heavy black smoke billowed from the substation as neighbors in the area described on social media seeing the sky turn orange following a loud explosion. San Juan Mayor Carmen Cruz tweeted that no injuries had been reported and that firefighters were on the scene.
The blackout comes as more than 400,000 power customers remain in the dark more than five months after Hurricane Maria. The Category 4 storm destroyed two-thirds of the island's power distribution system and caused up to an estimated $94 billion in damage.
Puerto Rico's governor recently announced that he plans to privatize the state-owned power company, which is $9 billion in debt and relying on infrastructure nearly three times older than the industry average. It would be the largest restructuring of a public entity in U.S. history.