Puerto Rico's power grid broke down again on Thursday, leaving some 800,000 customers without power, as the US Caribbean possession struggles to recover five months after Hurricane Maria slammed the island. Justo Gonzalez, head of the Puerto Rico Electric Power Authority (PREPA), said that one of the island's main transmission lines was out of service. The government-owned utility has 1.5 customers out of a population of 3.5 million -- not counting the 500,000 Puerto Ricans who left since Maria struck on September 20, 2017.