SAN JUAN (CBSNewYork/AP) — A blackout hit northern Puerto Rico late Sunday after an explosion set off a major fire at a main power substation in the U.S. territory.

Officials with Puerto Rico Electric Power Authority said late Sunday that several municipalities are without power, including parts of the capital of San Juan. It was not immediately known what caused the fire.

Heavy black smoke billowed from the substation as neighbors in the area described seeing the sky turn orange following a loud explosion.

San Juan Mayor Carmen Yulín Cruz tweeted that no injuries were reported yet and that firefighters went to the scene. As of around 9:15 p.m., Cruz tweeted that it appeared the fire had been almost totally extinguished, and there were reports that parts of San Juan were getting electricity back.

The blackout comes as more than 400,000 power customers remain in the dark more than five months after Hurricane Maria.

Puerto Rico Gov. Ricardo Rosselló recently announced that he plans to privatize the state-owned power company.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)