DaimlerChrysler on Thursday said it was investing about $US600 million in expanding its Mercedes-Benz M-class SUV plant in Tuscaloosa, Alabama, according to Reuters. As a result, the workforce would be doubled to about 4,000 employees and annual production capacity at the 10-year old factory also will be doubled to about 160,000 vehicles, the company said in a statement cited by the news agency.