A spokesman for the Transportation Safety Board said the Canadian bulk carrier CWB Marquis went aground on Friday after hitting a large floe of ice.
The TSB sent a team of investigators to the site by mid-afternoon, where they started interviewing crew members and assessing the ship's condition.
A spokesman for a marine services company has said that two of its tugboats are at the scene and have begun evaluating how to move the carrier.
The St. Lawrence Seaway Management Corp. says the vessel is owned by CWB, the former Canadian Wheat Board.
According to a post issued earlier this year by the ship's management company, it was loaded with more than 29,000 tons of Labrador iron ore.
It was expected to carry both grain and ore and play a strategic role in an integrated grain handling system, according to a news release the CWB issued last fall.
It is not yet known whether the ship has been damaged.
Its departure Thursday through the St. Lambert Lock marked the official opening of the Seaway's 57th navigation season.
Last year, 40 million tonnes of cargo moved up the Great Lakes/St Lawrence Seaway.