General Motors (NYSE:GM) has increased its previous commitment of $183 million by an additional pledge of $167 million, bringing its planned investment in its Spring Hill, Tenn., assembly plant to $350 million, the company announced today.

The planned investment is for two future mid-size vehicle projects, which will create or retain approximately 1,800 jobs total, according to GM.

"Today's announcement recognizes the commitment of Spring Hill employees and leadership," said Mark Reuss, president, GM North America, in the company's statement. "As a team, they draw upon the plant's unique heritage and dedicated work force to deliver top quality for our customers."

The Spring Hill facility is 40 miles south of Nashville and is a flexible-assembly plant that can be retooled to produce different types of vehicles to meet changes in demand.

The plant had been the home of General Motors' Saturn brand from 1990 to 2007. Since 2012, it has been producing the Chevrolet Equinox. The company did not give any information on the timing of the projects or on the specifications for the future vehicles.

The Spring Hill assembly plant had been idled amid the economic downturn in 2009, but production was restarted following a 2011 contract agreement with the United Auto Workers that included salary concessions for entry-level workers. At its peak, the facility employed nearly 8,000 workers. By 2009, that number was down to about 630. The plant, which also makes four-cylinder engines, currently employs 2,000 people.

-- Material from The Associated Press was used in this report.