Pockets of Cuba's capital Havana saw the lights flicker back on though vast areas of the city and country continued without electricity on Sunday morning, after a nationwide grid collapse that knocked out power to 10 million people.

The blackout began when a transmission line at a substation in Havana shorted, triggering a chain reaction that caused the entire island's power generation to shut down. This incident marked the fourth nationwide blackout since October.

Cuba has suffered a massive power outage affecting Havana and the country’s provinces that has left millions in the dark.