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

(U.S. Coast Guard)

An unknown sheen has appeared in Lake Ontario, and the Coast Guard is investigating the area.

The sheen was reported to officials Sunday when it was seen near the Fitzpatrick Nuclear Power Plant in Scriba, New York, some 40 miles north of Syracuse.

A Coast Guard Auxiliary air crew had noticed it during a flight and reported it. The cause is unknown.

The Coast Guard says it has set up a temporary safety zone extending two miles to the north and two miles to the east and west from the power plant.

A boat crew has taken samples of the sheen, and is enforcing the safety zone.

The New York State Department of Environmental Conservation also is on the scene.