Four companies are planning to hire more than 10,000 workers for new homeland security-related jobs in Virginia over the next five years, Gov. Mark R. Warner is to announce today.

Warner (D) is expected to make the announcement in a ceremony at the Herndon campus of Booz Allen Hamilton Inc., one of the companies planning to expand its presence in the state, according to government sources who spoke on the condition of anonymity before the governor's event.

The jobs Warner is to announce today, most of them in information technology, will be new to the Washington area, the sources said, adding to the region's growth in employment tied to post-Sept. 11 government spending on homeland security and defense.

The added jobs will be primarily in Fairfax County, Arlington and Alexandria, although some will go to Charlottesville and Norfolk, according to a source in state government.

After the dot-com bubble burst, many Northern Virginia companies went out of business and thousands of local technology workers were handed pink slips. The area's technology sector still faces occasional setbacks, such as plans by America Online Inc. to cut more than 700 jobs in December, mostly at its Northern Virginia headquarters.

But the increases in spending on homeland security and defense have fueled a resurgence in the region's technology industry, said Stephen S. Fuller, a professor at George Mason University who studies the region's economy. "Northern Virginia is getting a very big boost because of the war on terrorism and other related federal spending, Fuller said. "We're adding new jobs and getting better jobs . . . and the multipliers are higher, so we're adding more construction and retail jobs."

Executives with Booz Allen Hamilton, which has about 10,000 employees in the greater Washington area, declined to comment on the planned expansion in Virginia.

Officials from the Fairfax County Economic Development Authority and the governor's office declined to name the other companies planning expansions. Two of the four have headquarters in Northern Virginia, and all have a presence in the area, one source said. One of the firms is a financial services company that will work in the homeland security sector, while the rest of the new jobs will be technology-related. One building is to be constructed to accommodate the expansion, and one other construction project is to be launched. Existing offices will absorb the rest.

Including the jobs to be announced today, more than 35,000 new homeland security and defense sector jobs have been created in Virginia since the Sept. 11, 2001, attacks. During that time, more than $1 billion in related capital investments has been made in the state by federal agencies and the private sector.

In Northern Virginia, 59,000 professional service jobs in all sectors were created between September 1999 and September 2004, according to the Bureau of Labor Statistics. More than 141,500 jobs were created in the area during the same period.

In September, International Business Machines Corp. pledged to bring 1,250 new government contracting jobs to Fairfax County after the state and county committed $1.2 million in funding for improved roads and infrastructure. It is not clear if similar deals were brokered to lure the four companies to expand in Virginia, but all of them will qualify for the state's "major facility job tax credit," which applies to any business that creates at least 100 new full-time jobs as it expands.

Warner is to be in Northern Virginia on Friday to announce the relocation of two corporate headquarters to the region. CGI-AMS, the U.S. unit of CGI Group Inc. of Montreal, plans to make its existing operation in Fairfax its U.S. headquarters at a ceremony there. AgustaWestland, a helicopter manufacturer based in Italy and the United Kingdom, is to announce Friday that it is moving its U.S. headquarters to Fairfax County. The company is moving a small staff from Crystal City but may expand if it wins a contract to replace the Marine One fleet of presidential helicopters.

Staff writer Michael D. Shear contributed to this report.