Messages left Monday with Toyota and the UAW were not immediately returned.
Toyota Motor Co. said earlier this month that it will spend $250 million assisting employees at the factory.
Nummi, which stands for New United Motor Manufacturing Inc., began 25 years ago as a joint venture between Toyota and General Motors Co. The goal was to let GM observe the Japanese car-making system and let Toyota test out its production model on U.S. workers.
GM, which briefly went into bankruptcy protection last year, pulled out of the alliance and is liquidating its stake. Toyota announced in August that without GM, it could not sustain the factory and it would halt production.
Toyota plans to move production of the Corolla sedan to Canada and Japan and the Tacoma pickup to Texas.
The UAW represents the Nummi workers because of its history with GM. The union doesn't represent any other Toyota workers in the U.S.