Reactor Number 3 returned to service Thursday at the Indian Point nuclear power plant in Buchanan.

Officials from Entergy, the company that owns and operates Indian Point, say water levels inside a steam generator began fluctuating so operators manually shut down the unit Wednesday afternoon. They say one of the unit's pumps, which is part of the system that feeds water into the plant's steam generators, automatically shut down while the unit was operating at full power and that's what caused the water levels to fluctuate. The pumps are located on the non-nuclear side of the plant.

This is the same unit where the main transformer exploded and caught fire back in May, sending thousands of gallons of oil into the Hudson.

There was another shutdown last month when a balloon reportedly got tangled in electrical wires at the plant.

Entergy officials say Reactor 2 continued to operate at full power.

Units 2 and 3 generate approximately 2,000 megawatts of electricity, and supply about 25 percent of power used annually by homes, business and public facilities in New York City and Westchester.