DULUTH  — Thick ice on Lake Superior is causing shipping delays, with about 60 ships waiting to enter the area, according to the Coast Guard.

The ships are “certainly not delivering the raw material at the frequency that the facilities need,” said Mark Gill, director of vessel traffic services for the Coast Guard at the Soo Locks between Lakes Superior and the lower lakes. “That’s put a drain universally on steel production, power production, grain shipments, and many other industries that suffer as a result of that.”

Lake Superior is still about 60 percent ice covered, Gill said. Three heavy ice breakers are escorting convoys of five ships across the lake, where wind-blown ice is still 8 feet thick in places.

The season’s first trip from Duluth to lower Lake Michigan took two weeks. It normally takes less than three days. Some steel mills and power plants around the Great Lakes have run low on supplies of iron ore and coal.

Gill hopes convoys will only be needed for another week to 10 days.