Fairfax officials have discovered that almost 7,000 acres in a prime development corridor near Fair Oaks Mall could be embedded with pockets of naturally formed asbestos, triggering a sensitive public relations problem in the booming county.

County officials said they have identified airborne asbestos at two construction sites, a public high school and an office building. The material found so far does not pose a health threat because the airborne fiber content is very low, according to state and county officials. Some officials maintained in recent interviews, however, that the extent of the problem may be greater.

A county soil scientist who took more than 30 test samples from the asbestos-bearing rock formation that runs throughout the west-central portion of Fairfax said the formation lies in an area where a number of commercial and residential construction projects are under way or planned, including a portion of the Little Rocky Run subdivision.

"This area is between Fair Oaks Mall and Rte. 50, a large development corridor. That area down there is supposed to be another Tysons Corner," said scientist Mark Plank.

"There's no question that there is some asbestos in the rock," said Plank, who is with the county's Department of Extension. "The county is definitely concerned. They are concerned because the area that is asbestos-bearing is an area soon to have development in it. We're concerned about the health aspect of workers."

County and state officials have said that based on preliminary findings, there is no immediate hazard, but the county has been reluctant to release details of their findings or plans. Calls to various county agencies with knowledge of the asbestos threat were being referred to the county's public affairs office. Several county officials refused to comment or did not return a reporter's telephone calls. The county's Department of Environmental Management, which handles development plans, is not accepting calls to discuss the matter.

And last week, county officials decided not to pursue their plans for further air sampling, leaving it up to the state to set guidelines.

There is dispute about whether the asbestos is hazardous. "It's tricky," said Environmental Protection Agency spokeswoman Alicia Tenuta. "It's naturally forming, for one . . . . And it's not in an enclosed area. We really don't have regulations."

Plank said the rate of asbestos found in the rock samples ranged from less than 1 percent to possibly as high as 85 percent, based on the results he had seen.

The EPA considers more than 1 percent asbestos content in building materials to be a potential health threat, but the agency does not have regulations dealing with rocks.

Fairfax and state officials said the amount of fibers released in the air from the formation is not high enough to be governed by federal or state regulations. When breathed in large amounts over a long period, asbestos can cause cancer.

The airborne fiber count at the Fairfax sites was measured at 0.003 and 0.004, lower than the 0.2 fibers per cubic centimeter that is considered permissible exposure, according to Clarence Wheeling, the health enforcement director of the state Department of Labor and Industry.

But with the higher percentage of asbestos content in the rock, Wheeling said, "you have a better chance of generating more fibers."

The actinolite asbestos was found in a band of rock that spans roughly 10 square miles, taking a sinuous course from Miller Road, about two miles north of Fairfax City, and ending about eight miles southwest of Fairfax City.

While actinolite, one of six minerals called asbestos, is not generally fibrous, the mineral in this case has become fibrous because the rock formation in which it is embedded is highly deformed, according to Malcolm Ross, a research mineralogist for the U.S. Geological Survey, a part of the Interior Department.

The asbestos problem came to light during recent construction activities, which disturbed the asbestos-contaminated rock formation.

Plank said he took samples from the rock formation about five weeks ago, after work was suspended at the construction site of Fair Oaks Commerce Center, near Rte. 50 and Waples Mill Road. Work also was temporarily suspended at the Braddock Park High School construction site, off Braddock Park Road on Union Mill Road, about one month later.

The soil scientist, who was reached by telephone at his home Saturday, said he was unaware of the county's next move because he was out of the office last week attending a training session in Arlington.

"It's a political decision," said Plank, explaining that his role was to collect technical information. "Do they want to close down the development or let everything go as if nothing is a problem?

"From here on, it becomes a decision done by people higher up than me. At some point in time, someone is going to have to make a decision on the issue."

The public issue of asbestos has focused on regulations in such places as schools, but the laws on how to deal with potentially dangerous fibers found during construction work, as in Fairfax, are unclear, officials said.

"It's a real unusual situation," Plank said. "This rock type occurs in other areas besides Fairfax, but those areas are primarily agricultural areas. What we do probably will be a guideline for what other areas do when other areas develop."

County officials last Wednesday met with three state environmental regulatory agencies to assess the potential hazard of naturally formed asbestos found at the construction sites. Both sides agreed there appeared not to be a problem and also agreed more information was needed.

Afterward, Fairfax officials said the county would present more data to state officials and present a plan to sample asbestos.

On Friday, however, Deputy County Executive Denton Kent said in an interview that the county plans no further testing. He said the county would continue to monitor the wetting down of the ground at the sites -- a standard precaution that prevents dust from spreading and reduces the potential release of asbestos.

Kent said he did not know the extent of the problem but said a county task force on asbestos had concluded the county had no authority to take on air quality enforcement and would wait for guidance from the state.

An official with the Washington Building and Construction Trades Council, which represents 18 construction unions in the Washington area, said he is not surprised by the county's response.

"They probably don't want to find out if it's a big problem," said Jerry Lozupone, the council's safety coordinator. "It's very frustrating to deal with this. Everybody tries to put the burden on someone else."

At the State Air Pollution Control Board, asbestos coordinator Jim Lehan said a major concern expressed by county officials was whether the asbestos threat would affect contractors' ability to obtain liability insurance.

"They seemed to be concerned about the insurance aspect, also their own," Lehan said. "How it will affect development. You can't build a building if you don't have liability insurance."

Lehan was among a group of state officials who met with the Fairfax delegation, which included the directors of the county's Department of Environmental Management and the health department's air pollution control division. The consensus was that the asbestos problem appeared not to be dangerous.

"I told them, assuming they do sampling and the results stay where they are now, they have a bigger public relations problem than anything else," said Wheeling, with the state Department of Labor and Industry.