A Toyota spokeswoman confirmed Thursday that Toyota's board voted earlier in the day to end the company's contract.
The plant was established in 1984 and employs 4,600 workers. Toyota builds the Corolla compact car and Tacoma pickup trucks at the plant.
NUMMI works with 1,186 different supplier companies. All but 5 are them are in California. The businesses employ an estimated 20,000 people.
The NUMMI plant's fate was thrown into question in June when General Motors announced it was withdrawing from the 50-50 joint venture as part of its bankruptcy.
Japanese media outlets reported Wednesday that Toyota would slash worldwide capacity by 700,000 to 1 million vehicles.
A Fremont Chamber of Commerce official said the decision is "a devastating blow" to the city and the state.
"The loss of NUMMI is a huge blow to our regional and state economies and the families of the workers at the plant," the chamber's government and community affairs director Nina Moore said.
A spokesman for Toyota Motors said the company will issue a statement on the decision sometime Thursday.
NUMMI spokesman Lance Tomasu wasn't immediately available for comment, nor were officials at United Workers Local 2244, the union that represents the people who work at the plant.
Moore said that in addition to the NUMMI workers who face the prospect of losing their jobs, California will face an estimated loss of 35,000 jobs directly and indirectly because the closure of NUMMI will affect companies that are suppliers for the company or do business with the plant in other fashions.
Toyota officials said they expected to make a decision by the end of August.
NUMMI is a 25-year-old joint venture between General Motors and Toyota.