Matson Inc., the transportation company responsible for a molasses spill that killed more than 26,000 fish and other marine life in Hawaii, says it has been subpoenaed by a federal grand jury for documents relating to the spill. The company said it was served with a subpoena yesterday and received written requests for information on the spill from two state agencies and the U.S. Environmental Protection Agency. The spill of 233,000 gallons of molasses happened in early September in Honolulu Harbor.  Matson says it doesn't yet know how much the spill may cost the company.