The fire has since been put out and there are no ongoing emergency threats, according to the officials.
Indian Point Energy said there was no danger to employees or the public and that Unit 3 of the facility safely shut down as designed after the transformer failed.
"Saw a huge ball of black smoke and then alarms audible across the river," said Gustavus Gricius, who witnessed the explosion.
Dave Lochbaum, who is the director of the Nuclear Safety Project, said the transformer is in the switch yard outside the plant, but within the security perimeter.
He said oil is used to cool the transformers and that an electrical short may have caused the explosion.
"Transformer explosions are not uncommon -- they happen roughly three or four times a year across the industry," he added.
Keep up to date with what’s happening in Turkey,
it’s region and the world.
You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.