DULUTH, Minn. (AP) — Officials say the expected departures of six vessels this week will mark the start of the 2018 commercial shipping season in the Twin Ports of Duluth, Minnesota, and Superior, Wisconsin.

The Duluth Seaway Port Authority says departure times are hard to pinpoint, but the first two vessels plan to leave their winter berths on Tuesday. They include a tug, as well as a freighter that will head for Two Harbors to load iron ore. Four other ore boats are expected to leave Thursday and Friday.

Once loaded, the ore boats will proceed across Lake Superior toward Sault Ste. Marie, Michigan, to await the opening of the Soo Locks at 12:01 a.m. on Sunday. Duluth-Superior could see its first arrivals a day or two later, depending on ice conditions.