It’s official. PACCAR Inc. plans to build a $400 million engine manufacturing plant in Columbus.

PACCAR, a publicly traded Fortune 200 company, was the name floating around when lawmakers met in special session last month to pass an incentive package aimed at bringing jobs to north Mississippi, but no one was willing to publicly confirm the speculation.

Gov. Haley Barbour held a news conference Friday in Columbus to make it official.

PACCAR, of Bellevue, Wash., is the maker of Peterbilt and Kenworth trucks. Production at the new plant could start by 2010 and officials say it will employ hundreds of people with an estimated payroll of $18 million.

“The creation of 500 new jobs and the public and private investment in Lowndes County will contribute significantly to continued economic growth here in Northeast Mississippi,” Barbour said in a news release. “I am pleased with the decision of this major international company to locate here, which is further testament to the tremendously skilled work force and can-do attitude at every level in this region.”

Construction on the 400,000-square-foot plant is scheduled to begin this year. The facility will produce 12.9-liter and 9.2-liter diesel engines for Kenworth, Peterbilt and DAF, a news release on PACCAR’s Web site said.

“PACCAR is pleased to locate its engine facility in one of the most dynamic and progressive areas in the Southeast,” Mark Pigott, chairman and chief executive officer, said in the new release. “The Columbus, Mississippi site provides superb proximity to our dealers, customers and strategic supplier partners.”

Barbour signed into law three incentive bills related to the project that lawmakers approved during a special session April 27. The incentive package totals $48.4 million for the Lowndes County project. The incentives package is for funding onsite improvements on roads, site preparation and the extension of water and wastewater services, as well as offsite items like infrastructure and work-force training.

The bills allow Lowndes County to issue $15 million in bonds and use eminent domain to obtain property for the plant.

“We appreciate the outstanding support from the State of Mississippi and Lowndes County in partnering with PACCAR to bring this significant economic investment to the area,” Richard Bangert, PACCAR’s vice president, said in a news release. “We look forward to developing a close relationship with Mississippi State University and regional community colleges by investing in their advanced engineering programs, as well as providing ongoing educational opportunities for our employees.”