By STEVEN DUBOISPORTLAND, Ore. (AP) â¿¿ A Pacific Northwest grain terminal owner imposed a lockout on longshoremen Wednesday after saying an "independent former FBI investigator" determined a union leader sabotaged company equipment at the height of contentious labor problems in December. United Grain Corp., part of the Japanese conglomerate Mitsui & Co., said nonunion replacement workers will operate its Vancouver, Wash., export terminal for an "indefinite" period. The company said it 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. "Deliberate attempts by an ILWU leader to damage equipment, disrupt operations and put co-workers at risk cannot be tolerated," United Grain CEO Gary Schuld said Wednesday. The union called the company's allegations unfounded, and locked-out longshoremen immediately picketed outside the terminal. Local 4 ranks third in membership on the Columbia River with 177 longshoremen and 109 part-time dockworkers, according to its website. "United Grain and its Japanese owners at Mitsui have failed to negotiate in good faith with the men and women of the ILWU for months, and instead chose to aggressively prepare for a lockout, spending enormous resources on an out-of-state security firm," ILWU spokeswoman Jennifer Sargent said in a statement. "Mitsui-United Grain has fabricated a story as an excuse to do what they've wanted to do all along, which is to lock workers out instead of reach a fair agreement with them." Late last year, the company was among Northwest terminal owners who declared an impasse on labor negotiations and imposed a contract that included new, management-friendly workplace rules. United Grain said the sabotage occurred Dec. 22, days before the impasse. In one case, someone shoved a 2-foot-long metal pipe into a conveyor, causing it to shut down, the company said. In another, a vandal damaged a gear box with a mixture of sand and water.