HUNTSVILLE, AL—Mazda Toyota Manufacturing (MTM), a joint venture between carmakers Mazda and Toyota, have significantly increased their previously announced investment to build a new assembly plant here.

MTM is investing another $830 million in the state-of-the-art factory, bringing its total cost up to $2.31 billion. That compares with the $1.6 billion price tag initially announced in 2018.

Production is expected to begin next year, eventually ramping up to assembling 150,000 Mazda crossover vehicles and 150,000 Toyota SUVs per year. The project has received more than $700 million in state and local government tax incentives.

Some 600 plant employees have been hired so far, and the factory will eventually employ up to 4,000 people.

As of the initial announcement, much of the facility’s infrastructure—siding, roofing, floor slabs, ductwork, fire protection and electrical—were 75 to 100 percent finished.