Cuban authorities say electricity is slowly returning to Havana and nearby provinces after a major disruption on Wednesday plunged large parts of the island’s west into darkness, marking another setback in the country’s prolonged energy crisis.

Energy officials reported that a key transmission line linking the capital to the main power station in Matanzas went down early Wednesday morning, triggering widespread outages. By midday, power had been restored to roughly 40% of Havana, while all affected western provinces from Pinar del Rio to Mayabeque were reconnected within hours.

The blackout added to the already severe daily outages residents endure. Many communities across Cuba routinely face 20-hour power cuts, while Havana once shielded from extended disruptions now experiences more than 10 hours without electricity most days.

Despite the grid reconnection, the government warned that electricity generation remains far below national demand, meaning regular blackouts will continue.

Before the latest incident, Cuba’s aging oil-fired plants had been operating under heavy strain, worsened by dwindling fuel shipments from allies such as Venezuela, Mexico and Russia. Crude and fuel imports between January and October dropped by more than a third compared to last year, according to shipping records reviewed by Reuters.

Officials have attributed recent grid failures to a combination of limited fuel supplies, outdated infrastructure and damage caused by Hurricane Melissa. The country’s deep economic challenges and long-standing U.S. sanctions have further restricted Cuba’s ability to purchase fuel on the global market.