Cuba’s electricity grid collapsed late on Sunday, the state-owned grid operator said, plunging the island of ‌about 10 million people into darkness as blackouts become more frequent.

According to Reuters, the outage follows three nationwide blackouts in July and comes as a U.S.-imposed oil blockade further strains the island’s ageing ⁠energy infrastructure.

Pressure on the power system has mounted as Cuba struggles to secure fuel imports.

It lost a key source of fuel after an oil blockade imposed by U.S. President ‌Donald ⁠Trump, following Washington’s January 3 ouster of Venezuelan President Nicolas Maduro.

Venezuela had long been Cuba’s primary oil supplier, with imports from Mexico also halted amid ⁠increased U.S. pressure.

The power crisis coincides with a cautious opening of Cuba’s tightly controlled energy sector, driven by ⁠fuel shortages and severe U.S. sanctions.

Havana recently authorized its first foreign-backed fuel import venture and ⁠allowed nearly 200 Cuban businesses to participate in wholesale fuel distribution.