Cuba's national electric grid collapsed on Monday, leaving around 10 million people without power.
The blackout is the latest sign of a deepening energy crisis caused by fuel shortages and the country's aging power infrastructure.
State-run grid operator Unión Eléctrica (UNE) is investigating the cause of the nationwide blackout.
The grid was already facing major power shortages before the full collapse, with a severe generation deficit of 1,891 megawatts on Sunday.
As of 6:00 AM Monday, the system had only 1,140 megawatts of available generation capacity against 2,347 megawatts of demand.
Authorities warned the situation could worsen during the evening peak period.
Several major thermal power units remain out of service due to breakdowns and maintenance work.
UNE said talks with the United States are underway to ease the crisis, but there is no timeline for the power grid's recovery.
