An Icelandic container ship was spilling oil in a Norwegian national park Friday after running aground and rupturing two 250-ton fuel tanks, authorities said.

The Godafoss hit ground late Thursday in the Hvaler national park after leaving the southern port of Fredrikstad, near the Swedish border, the Norwegian Coastal Administration said.

It wasn't immediately clear how much oil spilled into the icy water, but the oil slick reached shore on Friday, rescue spokesman Lars Erik Gutubakken said.

Crews placed a boom around the ship to keep more oil from reaching land. No one was injured in the accident.

The Norwegian Directorate for Nature Management said the area has a rich bird life, but it had not received any reports of birds affected by the oil spill.

"It's uncertain how many birds are there now and what consequences the oil spill will have on the nature," the agency said in a statement.

The cause of the accident had not been established Friday. Pictures from the scene showed the listing ship surrounded by rescue vessels, about 200 yards (meters) from the shore.

The Hvaler national park was established in 2009, some 60 miles (100 kilometers) south of Oslo, to protect an underwater ecosystem containing corals and kelp forest. It's Norway's only marine national park and is home to some 130 endangered plant and animal species, according to its website.