Blackout hits northern Puerto Rico following fire, explosion

SAN JUAN, Puerto Rico — 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