Sept 30 (Reuters) - Toyota Motor Corp (7203.T) and Mazda Motor Corp"s (7261.T) joint venture factory in the United States will hire 1,700 additional employees as it ramps up production, the companies said on Thursday. Mazda Toyota Manufacturing, which has started making the 2022 Toyota Corolla Cross model, expects to have 4,000 workers in total by next year, when production of the yet-to-be-announced Mazda vehicle will also begin. The JV expects to produce 150,000 future Mazda crossover vehicles and 150,000 Toyota sport utility vehicles annually. Last year, Toyota and Mazda increased their investment in the JV by $830 million to $2.3 billion.