Cuba’s electrical grid went offline Friday after one of the island’s major power plants failed, the energy ministry said.  

The massive outage left millions of Cubans without power and prompted the government to implement emergency measures to slash demand, including suspending classes, shutting down some state-owned workplaces and canceling nonessential services.

The government announced that one of the nation’s main thermoelectric plants, La Antonio Guiteras, had ceased operations at about 11 a.m. local time, with authorities saying it was only offline temporarily.  

Cuban officials said that the blackout, which started late Thursday, saw 1.64 gigawatts go offline during peak hours in the early evening, about half the total demand at the time.

The government was still working to restore service by Friday afternoon. “From the highest levels of the state we are working to solve this energy contingency as soon as possible,” Prime Minister Manuel Marrero posted on social media. “We will not rest until service is restored.” 

Earlier in the day, Marrero said in a special address on national television that the government had been “halting economic activities to ensure energy for the population.”

During his address, Marrero was accompanied by Alfredo López, chief of the state-owned utility, UNE, who said the outage stemmed from increased demand from small- and medium-sized companies and residences’ air conditioners, as well as breakdowns in old thermoelectric plants that haven’t been properly maintained, and a lack of fuel to operate some facilities.

The Energy Ministry posted on social media around 4 p.m. Eastern Time that it was still reviewing all thermoelectric plants, fuel availability and the state of the power grid. 

“There is not a defined timeline for total power restoration, but we are working to reconnect the electric system as soon as possible,” a ministry official said in a video posted on social media.

Changes to electricity rates for small- and medium-sized companies, which have proliferated since they were first authorized by the communist government in 2021, are also being considered, Marrero said.

Marrero sought to placate people’s concerns about the outage, citing an expected influx of fuel supply from Cuba’s state-owned oil company.

Even in a country accustomed to frequent outages amid a deepening economic crisis, the size of Thursday night’s blackout left millions of Cubans on edge. Residents shut their doors and windows, which they typically leave open at night, and candles or lanterns were visible inside homes.