Feb. 12 (UPI) -- Puerto Ricans were plunged into darkness again Monday after an explosion and fire at a power substation, officials said.
Puerto Rico Electric Power Authority, or PREPA, spokesman Carlos Monroig told CNN the explosion Sunday affected parts of San Juan, Trujillo Alto, Guaynabo, Carolina, Caguas and Juncos.
The island's electric power authority tweeted that around 400 megawatts of power generation were lost.
The blackout largely affected the northern part of Puerto Rico, just months after Hurricane Maria cut power to the entire island.
Crews have been working for months to restore the electrical grid.
San Juan Mayor Carmen Yulin Cruz said no casualties were reported from the explosion of fire.
Last month, Puerto Rico Gov. Ricardo Rossello announced the island would privatize the assets of PREPA and bring investment back to the island after the devastating hurricane.