All but two of 47 families were permitted to return to their Centreville subdivision last night after authorities pronounced the neighborhood safe from the effects of Thursday's massive gasoline leak.

While authorities emphasized that cleanup efforts would continue for weeks, they said there was no longer a threat of explosion from the spill, which occurred when a bulldozer tore open a 32-inch underground pipeline and triggered a 100-foot geyser of high-test unleaded fuel that rained on houses, cars, trees and sidewalks in the Singleton's Grove subdivision in western Fairfax County.

"The fire department has tested the homes, basements and the electric sockets," said Claude Cooper, director of the department of environmental management in Fairfax, meeting with residents at the hotel where most of them have stayed since the rupture. "If we felt there was going to be any threat we would not tell you to go back this evening."

Cooper said that the residents of two homes nearest the spill would not be able to return yet, and warned parents not to let children or pets roam in gasoline-soaked areas that have been cordoned off.

Some residents expressed concern about the health effects of breathing gasoline vapors, but most seemed more interested in putting the episode behind them.

"We're probably going to move back in" today, said Kevin Hagan, an engineering technician who fled the spill with his wife and 9-month-old baby. "I want to get into the house before we let the baby in. I don't think the vapors are going to be a problem. I just want to make sure."

The neighborhood they return to will look and smell different than it did before the incident occurred.

Gasoline fumes, while no longer concentrated enough to be considered ignitable, have infused the area with the aroma of a service station.

Grassy strips in front of Singleton's Grove's town houses have turned from springtime green to autumnal brown. A stand of trees adjacent to the model homes near the entrance of the subdivision has the drooping, lifeless appearance of a Hollywood haunted forest.

Not as perceptible, but still in the air, is the lurking remembrance that just one small spark Thursday morning could have torched the entire area, leaving no homes, no trees, no life.

"It could've been much, much worse," said Fairfax firefighter Jimmy Ghi, who was testing vapor levels in the area yesterday afternoon. "We could have had bodies all over the place up here."

Early yesterday, welders replaced a 14-foot length of the damaged underground pipe. By 4 a.m., liquid petroleum products were again coursing through the pipe, which runs from North Carolina to the Baltimore area.

In the afternoon, workers were dumping gasoline-free soil over the exposed section of pipe, which under federal regulations must be at least 30 inches underground.

Electricity was turned back on in the subdivision yesterday.

Firefighters continued to spray fire-retardant foam over parts of the subdivision. As the foam evaporated in the hazy sunshine, they reapplied it.

State authorities brought a 7,000-foot absorbent boom from Norfolk to place in Bull Run, a nearby stream that feeds the Occoquan Reservoir, which supplies water to more than 600,000 Northern Virginians.

Authorities hope that the boom, in addition to some hastily built dams and continuing vaccuming, will help keep gasoline from running into the reservoir. Officials said that while rain could cause some gasoline to run off into streams, they remain confident that there is no threat to drinking water from the reservoir.

"It hasn't even broken through our first line of defense so far," said Pam Wieger, spokeswoman for the Fairfax County Fire and Rescue Department.

Consultants hired by US Home, developer of Singleton's Grove, were testing soil in the area to determine how much needed to be carted away.

Friday night, the federal Environmental Protection Agency stepped in, charging the pipeline owners, Colonial Pipeline, with responsibility for the cleanup.

That bureaucratic step relieved Fairfax County of any fiscal burden arising from the project. Under the U.S. Clean Water Act, Fairfax now has the authority to direct and augment the utility's cleanup efforts with the assurance that the county will be reimbursed with federal funds.

There was no new word yesterday on where fault may lie for the accident, which dumped thousands of gallons of gasoline on the area. A federal official said Friday that preliminary indications point to a mistake on the part of the bulldozer operator, Keith Carpenter, 37.

Carpenter could not be reached for comment yesterday. However, James E. Pinkowski, an attorney for F.E. Gregory & Sons, the firm that owns the bulldozer, told The Washington Post that Carpenter "is taking the position that the pipe was higher than it was supposed to be."

He added that Carpenter, a foreman, had coordinated all construction at the site with Colonial, the pipeline owners.

"The representative from Colonial knew they were working in that area," said Pinkowski. "Keith has been working around the pipe for six to eight months now."

Pinkowski added, however, that he did not want to comment definitively on the incident until investigations have been completed.

About 75 people attended the meeting at the Fair Oaks Holiday Inn last night, where they listened to assurances from Fairfax County Supervisors John Herrity and Elaine McConnell, environmental and fire officials and representatives of US Homes.

Cooper warned residents to expect damage to shrubs and other plants, and advised against eating produce from vegetable gardens contaminated with gasoline. "Consider it gone for this year," he said.

He also advised, "If you have a vehicle, air out the garage before you start it."

Cooper told residents to call authorities if they notice vapors permeating their homes, or if their drinking water tastes unusual.

Most people seemed to take the episode in stride. One enterprising resident had already printed up a T-shirt commemorating the event with the slogan, "I Survived the Rupture."