HAVANA — Power was restored to millions of people early Monday after a blackout that cut the lights in much of western Cuba, including the capital Havana.

Electricity began to return to the capital at about 1 a.m. and the entire city was back online by morning.

Cuba's Ministry of Basic Industries said the problem occurred in a 220,000 volt transmission line that runs between the central cities of Ciego de Avila and Santa Clara, though the cause was not clear.

Cuba's electric company warned Monday that further interruptions might occur at peak hours throughout the day, but that it hoped to have normal service restored by Tuesday.

The power outage struck just after 8 p.m. Sunday during a sweltering late-summer night.

The blackout affected communities from Pinar del Rio, in the west, to Ciego de Avila and Santa Clara in the center of the country. The grid came back online from east to west, with neighborhoods of Havana returning in stages early Monday.

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