A grain terminal owner says it has uncovered sabotage by a Longshore leader and will lock out members of the union from its terminal in Vancouver, Wash.

United Grain Corp. said Wednesday it has fired the union leader, whom it described as a member of the bargaining team of Local 4 of the International Longshore and Warehouse Union but did not name.

The union called the company's allegations unfounded and a fabrication.

Late last year, the company was among Northwest terminal owners who declared an impasse and imposed a contract on many of the workers who handle a quarter of U.S. grain exports.

United Grain said in a statement that a private investigation turned up evidence of sabotage in December of conveyor and gear systems.