(Reuters) - Parts of northern Puerto Rico on Sunday were left in the dark after a mechanical failure caused a fire at a power substation, CNN reported, citing authorities.

The fire impacted sections of San Juan, Trujillo Alto, Guaynabo, Carolina, Caguas, and Juncos, CNN reported, citing Puerto Rico's Electric Power Authority (PREPA) spokesman Carlos Monroig. cnn.it/2BUHjJG

“It appears fire has almost totally been extinguished and the cooling phase is beginning. No injured reported,” San Juan Mayor Carmen Yulin Cruz said on Twitter.

The majority of customers would have power restored Sunday night, Monroig told CNN. Communities powered by substations Villa Betina and Quebrada Negrito would likely be without power until Monday afternoon, he added.

CNN reported that 400 megawatts of power generation had been lost, citing a tweet posted by PREPA.

Reuters was not immediately able to reach PREPA for a comment.

Puerto Rico is struggling to recover from Hurricane Maria, which hit on Sept 20. The storm killed dozens and left the entire island without power at a time when it was already trudging through the largest government bankruptcy in the United States history, with some $120 billion in combined bond and pension debt.