BUCHANAN, N.Y. (CBSNewYork) — A generating plant at the Indian Point nuclear facility in Westchester County shut down Monday evening, prompting an immediate investigation.

Gov. Andrew Cuomo’s office reported that Unit 3 at Indian Point shut down at 7 p.m.

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The cause was unknown late Monday, but Cuomo reported that he directed the state Department of Public Service to investigate.

The operators of Indian Point said no radioactivity was released into the environment.

Control rods shut down just nine days ago at the Indian Point 2 reactor at the plant.

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Following that incident, opponents of the plant said Indian Point should close for good, pointing to a handful of mishaps this year including a transformer fire and water pump problem.

Indian Point reactors 2 and 3 are up for relicensing. The two reactors supply about one-fourth of the power for New York City and Westchester County.

Cuomo said Monday night that inspections at the plant would increase.

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“Because of the number of recent unplanned outages, the Nuclear Regulatory Commission’s requirements will result in increased inspections and scrutiny of the plant,” Cuomo said in a statement. “A thorough investigation of this shutdown is underway and we will make sure the safety of New Yorkers is not compromised.”