Puerto Rico remains without electric power

More than a million customers in Puerto Rico remained without electricity on Thursday after a fire at a main power plant caused the biggest blackout so far this year across the U.S. territory.

It forced to cancel classes and shutter government offices, left 160,000 without water and prompted traffic. Luma, the company that took over transmission and distribution from Puerto Rico's Electric Power Authority last year, said the blackout could have been caused by a circuit-breaker failure at one of four main plants on the island.

The outage occurred two months before the Atlantic hurricane season starts, worrying many about the condition of Puerto Rico's electrical grid. Emergency repairs were made at the time, but reconstruction efforts have not yet started, and power company officials blame aging, ill-maintained infrastructure for the ongoing outages.