Members of the Fairfax County Board of Supervisors said yesterday they are puzzled by the failure of the District's unemployed to fill the many vacant jobs in Northern Virginia, where some businesses have been importing laborers from as far away as North Carolina.

The supervisors agreed, however, that neither they nor the District government can do much to change the attitudes of either Northern Virginia employers or Washington residents.

"We can't force people to make decisions on who they hire," said Supervisor Audrey Moore, a Democrat.

"It's too bad, but there's nothing the county government can do about it."

"It's up to employers to seek out their help, not up to the county government," said County Board Chairman John F. Herrity, a Republican.

He said Washington residents are "certainly free to come over here," and Moore suggested there may be "a certain amount of racial bias" by the employers who are shunning Washingtonians.

But if Fairfax businesses fear District residents are not qualified to work on their projects, Board Vice Chairman Martha V. Pennino, a Democrat, asked: "Who is building those high-rise buildings and offices and beautiful hotels in the District?"

The supervisors comments yesterday were triggered by a news story in The Washington Post Sunday that discussed the abundance of blue-collar jobs in Northern Virginia and the inability of many firms to find laborers willing to fill them.

Many of the businessmen interviewed said the Virginia suburbs have become too costly for most laborers to live in and that residents of Washington, where there is high unemployment, are unwilling -- or unable -- to cross the Potomac River to work in Virginia.

In another action, the supervisors asked private developers for proposals on how they would commercially develop a 183-acre site, long planned for a new county government center.

Some supervisors also strongly attacked proposals for intense development around Metro stations -- an attack that appeared to focus on a proposal by developer John T. (Til) Hazel and others to build a 32-story complex around the Vienna stop.

The supervisors voted unanimously to seek the help of developers in beginning construction on county land at proposed county government site, near I-66 and Rte. 50, west of Fairfax City.

Herrity, who introduced the plan, said he has been contacted by "two or three" builders interested in developing the site with the county.

Last year, supervisors rejected an attempt to put the $71 million center up for referendum, and several supervisors said yesterday they still oppose including the proposal on the fall ballot this year.

Top Fairfax officials argue that the county, which pays $5 million a year in rental costs for office space in traffic-choked Fairfax City, badly needs a new government center.

A joint venture, in which Fairfax might grant some land at the site to a developer in return for construction of a new county building, is seen by some officials as a way of financing the project without resorting to public debt and higher taxes, the officials say.

Several supervisors criticized a group of developers who are planning to pay for a study on the benefits of intense development around the Metrorail stations scheduled to open in Fairfax in the next two years.

The study would be used in an effort to convince the Virginia General Assembly that it should not cut funding to the Metro system because the transit system provides the state with an economic boost.

Some supervisors said the county should have controlled the study.

The study is being paid for by developers, county officials said, because some legislators feared a county-funded study would be received skeptically in Richmond.