Ontario-based Algoma Central Corp says its Algoma Tankers unit has bought four tankers from Imperial Oil for C$13 million (about HK$70 million), which involves a long-term contract to transport Imperial Oil liquid products. Under the agreement, Algoma Tankers will transport Imperial products on the Great Lakes, the St Lawrence Seaway and the eastern coastal waters of Canada and the United States. Algoma owns and operates the largest Canadian fleet on the Great Lakes.