A sheen is seen on the water near Fitzpatrick Nuclear Power Plant in Scriba, New York, on June 26, 2016.

(U.S. Coast Guard)

The source of the mysterious sheen on Lake Ontario has been discovered.

Turns out, it's lubrication oil spilledby the Fitzpatrick Nuclear Power Plant, officials say. The oil reportedly isn't hazardous and has low potential health effects.

The U.S. Coast Guard observed the sheen Sunday near the plant in Scriba, New York, about 40 miles north of Syracuse.

An official from operator Entergy Corp. said Monday that the oil came from a tank that overfilled because of an equipment malfunction.

"It appears about were then drained through the plant’s discharge drain system to the lake," Nuclear Regulatory Commissionpublic affairs officer Neil Sheehan to the Rochester Democrate & Chronicle. "The company has placed oil-absorbent pads on the turbine building roof and has also stopped all circulating water pumps to eliminate any further discharges."

The oil has not affected plant operations, he said.