The 194 meter long bulk freighter Buffalo went aground on Lake Huron near Sarnia, Ontario, Canada.  The Buffalo was en route to Cleveland with a cargo of iron ore pellets when it suffered a malfunction with its propulsion system.  No reports of injuries, damage or pollution released.   Two tugs were dispatched to the scene to help refloat the bulk carrier.   The Unites States and Canadian Coast Guard were on scene monitoring the situation.  Authorities are conducting an investigation into the incident.