Cuba's electrical grid collapsed Sunday for the fourth time in 48 hours, a major setback in the efforts to restore power to exhausted residents.

"Some additional weakening is likely while Oscar moves across the mountainous terrain of eastern Cuba, but Oscar is forecast to be a tropical storm when it moves north of Cuba late today and then moves near the southeastern and central Bahamas on Tuesday," the hurricane center said Monday morning.

Tropical Storm Oscar is making it harder to restore power in Cuba after a massive, prolonged power outage that preceded the storm. Oscar is hitting a key region for power generation where at least two important power plants in the city of Holguín Santiago de Cuba are located.