BUCHANAN, New York - Part of a New York state nuclear power plant remained offline Sunday after a transformer fire created another problem: thousands of gallons of oil leaking into the Hudson River, officials said.

New York Gov. Andrew Cuomo said emergency crews were out on the water near Buchanan trying to contain and clean up transformer fluid that leaked from Indian Point 3.

"There's no doubt that oil was discharged into the Hudson River," Cuomo said. "Exactly how much, we don't know."

It could be weeks before Indian Point 3 is reopened again, said a spokesman for Entergy Corp., the plant owner.

The transformer at the plant about 30 miles north of midtown Manhattan failed on Saturday evening, causing a fire that forced the automatic shutdown.

Cuomo revealed Sunday that even after the blaze on the nonnuclear side of the plant was quickly doused, the heat reignited the fire that was again extinguished.

The governor said oil in the transformer had seeped into a holding tank that did not have the capacity to contain all the fluid, which then entered river waters through a discharge drain.

Joseph Martens, commissioner of the state Department of Environmental Protection, said measures were taken to keep the oil from spreading, including setting up booms over an area about 300 feet in diameter in the water.

The cleanup should take a day or two, Cuomo said.

A spokesman for the Nuclear Regulatory Commission said several thousand gallons of oil may have overflowed the transformer moat.

The reactor itself was deemed safe and stable, said Entergy spokesman Jerry Nappi. The plant's adjacent Unit 2 reactor was not affected and remained in operation.

The Indian Point Energy Center in Buchanan supplies electricity for millions of homes, businesses and public facilities in New York City and Westchester County.

"These situations we take very seriously. Luckily this was not a major situation. But the emergency protocols are very important," Cuomo said Saturday. "I take nothing lightly when it comes to this plant specifically."

The transformer at Indian Point 3 takes energy created by the plant and changes the voltage for the grid supplying power to the state.

The blaze, which sent black smoke billowing into the sky, was extinguished by a sprinkler system and on-site personnel, Nappi said.

He said a foam-like substance containing animal protein and fat was used to put out the fire, leaving an oily sheen on the water that does not harm the environment. He said he cannot confirm that fluid from the transformer leaked beyond the holding tank until a probe is conducted.

It was not immediately clear what caused the initial failure.

Officials did not know how long the 1,000-megawatt reactor would be down. Nappi estimated it could be "a few weeks" before Indian Point 3 reopened.

Cuomo said there had been too many emergencies recently involving Indian Point. Unit 3 was shut down Thursday morning for an unrelated issue - a water leak on the nonnuclear side of the plant.

In March, Unit 3 was shut down for a planned refueling that took about a month.

Diane Screnci, a spokeswoman for the US Nuclear Regulatory Commission, said an agency inspector was at the site Sunday and the agency would follow up as Indian Point assesses the affected equipment.

She said there was no impact on the public.

The environmental watchdog group Riverkeeper issued a statement Sunday saying the latest Indian Point accident proves that the plant should be closed for good.