Newton-based Maytag is expanding — to Mexico. The company will build a plant where workers will pre-assemble components of Maytag products, work that’s now done at existing Maytag plants or contracted out to other U-S companies.Maytag executives say competitors have been using Mexican labor to reduce the cost of the assembly process, putting Maytag at a competitive disadvantage. Maytag spokesman Jim Powell says they don’t know yet how this might affect jobs at the plant in Newton. He says they need to determine which assembly components can be put together at a lower cost in Mexico.Powell says there are lots of appliance industry plants in Mexico. He says Maytag’s Hoover division has had an operation in Mexico for about 17 years.The two million dollar Maytag plant in Mexico will open in the first quarter of next year — and will employ up to 230 people. A specific location’s not been chosen yet.