A ship carrying iron ore across Lake Superior collided with something underwater Saturday morning, puncturing the vessel and allowing water inside, the U.S. Coast Guard said.

The Michipicoten, a carrier ship longer than two football fields, began taking on water around 6:53 a.m. Saturday, the Coast Guard said. The ship is 35 miles southwest of Isle Royale and at least 22 people are on board.

Boat crews, a helicopter and the Edwin H. Gott are en route to the scene. Coast Guard officials said pumps aboard the Michipicoten have removed some water on board.

The ship is carrying taconite, a low-grade iron ore often mined from the Mesabi Iron Range. The Department of Natural Resources says those ships sail to Indiana, Ohio and other steel-making towns around the Great Lakes where it’s melted into steel.

None of the taconite on board the Michipicoten is believed to have spilled so far.