Puerto Rico's governor declared a state of emergency Thursday as power slowly returned to some of the 1.5 million islanders left without electricity after a power plant fire a day earlier.

About 200,000 customers had power restored by early Thursday afternoon, and officials hoped that number could double later in the day. It will be Friday before power is restored to all customers across the U.S. territory, Gov. Alejandro Garcia Padilla said.

The island has a population of about 3.5 million.

According to the Agencia Estatal para el Manejo de Emergencias y Administración de Desastres, two lines that transmit 230,000 volts were damaged in a fire at a power plant. The fire caused a cascade of problems thta knocked out the island's aging utility grid.

"Amid the general blackout ... several cell phone companies reported via Facebook that some customers may experience interruptions in telephone service because of this situation. This is the case of T-Mobile, Claro, Sprint and Open Mobile. Companies apologized for the inconvenience and said they are working with the situation," reported WAPA-TV.

The agency's Twitter page posted images of a fire at a plant in Central Aguirre that they say has been put out. At the moment, there is no cause to what started the fire.

According to the agency, the fire occured at a plant that is the largest electricity provider for the island. AEMEAD officials said the fire occurred where the plant's transformers are located.

Authorities say the outage caused 15 fires across Puerto Rico because of malfunctioning generators.

Many in Puerto Rico were forced to spend Wednesday night in darkness and without air conditioning. Most businesses and public offices were closed Thursday.

At least one person died overnight from exposure to carbon monoxide after setting up a generator, and a 76-year-old man was hospitalized after spending the night trapped in an elevator in a government building. He's expected to be OK.

"Puerto Rico is not prepared for something like this," said Celestino Ayala Santiago, who slept in his car so he could have some air conditioning.

Localized power outages are common on the island, but massive electrical failures typically only happen with tropical cyclones. The island territory has been suffering from crippling debt and is undergoing restructuring.

"This is an apocalypse," Jose Tavela said.

Information from Infomas and the Associated Press was used in this report.

Source: Graphiq