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.

Experts have attributed recent blackouts in Cuba primarily to fuel shortages, aging infrastructure and economic sanctions. Outside of Havana, many Cubans have experienced rolling blackouts for weeks.Millions of people in Cuba remained without power for a second night in a row on Saturday as the island nation dealt with a major power outage.

Power was slowly being restored across most of Cuba on Sunday, after nearly 40 hours without electricity, in the island's fourth major blackout in six months.