Cuba suffered another nationwide blackout on Friday, the second to hit the country in just one week. The latest outage highlights the growing strain on the island’s aging power system and ongoing fuel shortages.

Cuba’s Electric Union said a failure on a transmission line between the provinces of Santa Clara and Sancti Spíritus triggered the collapse. The fault caused instability across the national grid and cut electricity to most of the country. Crews quickly began restoring power, and some communities regained service within hours.

The blackout came only days after another islandwide outage on Monday. That disruption also affected nearly 10 million people. Friday’s incident marked the fourth nationwide power failure in Cuba this year. Earlier blackouts struck the country in March and parts of eastern Cuba in May.

Many of Cuba’s power plants are more than 30 years old. Years of limited maintenance have left the electricity system weak and unreliable. Fuel shortages have made the situation even worse. Without enough fuel, power stations cannot produce the electricity the country needs.

Prime Minister Manuel Marrero said the country has faced a very difficult week. He said several power units remain out of service, and fuel supplies are extremely limited. He also blamed what the government calls the United States’ energy blockade for adding to the country’s energy problems.

Fuel has remained scarce since January after the United States announced measures targeting countries that supply oil to Cuba. Since then, the shortages have affected many essential services. Public transportation has slowed, and hospitals have postponed thousands of surgeries because of the lack of reliable electricity and fuel.

Cuba produces only about 40 percent of the fuel it needs each year. The country received a shipment of Russian oil in late March, but officials said those supplies ran out by the end of April. To manage the shortage, authorities continue to schedule long power cuts in many communities. Some outages last more than 24 hours.

Officials continue working to restore electricity across the island after the latest blackout. The repeated power failures highlight the severity of Cuba’s ongoing energy crisis. As restoration efforts continue, millions of Cubans remain uncertain about when they will have a stable and reliable electricity supply again.