HAVANA - A large swath of Cuba was plunged into darkness on Sunday night in a widespread power failure, the cause of which was not disclosed.

Electricity went out from the city of Ciego de Avila in southeastern Cuba all the way to Havana, 250 miles (400 km) to the northwest, and beyond to the westernmost province of Pinar del Rio.

Phone calls around the island indicated power was returning in many areas, but not yet in the Cuban capital, which is the Communist country's biggest city with 2.2 million people.

There were unconfirmed reports that the outage was caused by the failure of a generating plant in Cienfuegos on Cuba's southern coast.

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