The growing gang problem in Northern Virginia is spreading to other parts of the state, migrating west into the Shenandoah Valley and south toward Charlottesville, officials said yesterday as they announced an infusion of federal money to fight it.

In an extraordinary show of concern, two U.S. attorneys joined numerous other federal and local law enforcement officials in Fairfax County, where they announced $500,000 in additional funds. The money, secured from the Justice Department by Rep. Frank R. Wolf (R-Va.), will be used by a gang task force in Northern Virginia that Wolf started and one in the Shenandoah region. The local task force will use its $350,000 share to fund programs in the schools.

Officials used stark terms in laying bare a Northern Virginia gang problem that escalated with the recent machete attack on a Fairfax youth and the gang-related shooting death of a Herndon teenager Sunday night by an assailant on a bicycle. Gang-related attacks, including slayings, beatings and rapes, have been more violent and prevalent in recent years in the suburbs of the nation's capital.

"This community sits at a crossroads,'' said U.S. Attorney Paul J. McNulty, whose office is based in Alexandria. "We can either go one of two directions from here. We will either slide into a greater problem of violence and degradation of our community as a result of gang violence, or we can focus more attention on the gang problem and bring it to a stop.''

In Herndon, more than 300 people packed the Town Council chambers last night, mostly to express concern about Sunday's shooting death of a 17-year-old high school freshman. Many residents, who were required to submit questions to officials in writing rather than ask them directly, were worried about rumors of potential retaliatory violence at Herndon High School and wanted to know what police were doing to prevent further attacks.

Janice Leslie, the school's principal, said the rumors were unfounded. Herndon Police Chief Toussaint E. Summers Jr. said the slaying did not mean that the town is engulfed in a gang problem, but he added that police patrols would be increased at the school and in the area where Jose Sandoval was shot.

After the meeting, residents said they were shocked that the region's rising gang problem had surfaced in their town. Others said they hoped the incident would not make people think that one ethnic group is responsible for all gang violence. "I'm concerned that this will shed a negative light on the Latino population," said Michelle Alvarado, a parent of two children at Herndon High.

Earlier yesterday, at a news conference at the Fairfax County Government Center, McNulty likened the fight against gangs to the war on terrorism. He said the same rules -- be proactive and look for the smallest signs to stop violence before it erupts -- apply to both struggles.

Much of the news conference was devoted to what officials called a growing pattern of gang members moving from Northern Virginia and the Baltimore area to more rural parts of Virginia.

The $150,000 for the Shenandoah gang and drug task force will help fund an influx of federal agents and prosecutors, who are fighting increasing drug trafficking and firearms use by gang members, said John L. Brownlee, the U.S. attorney based in Roanoke. He said gang members from the Washington area are attracted to other areas of Virginia, in part because they can sell drugs at a better price because the supply is lower.

"Some of you may think that out in the Shenandoah Valley and parts of the western district of Virginia, we don't have these kinds of issues, and unfortunately we do,'' Brownlee said. "We see the gang activity that has been homegrown here in the Northern Virginia area and Maryland migrating west and south to areas such as Winchester and on down into other areas of the Shenandoah Valley.''

Shenandoah County Sheriff Timothy C. Carter said officials there are seeing an increasing presence of gangs such as the violent Mara Salvatrucha, or MS-13. The body of a key witness in a federal gang murder case in Alexandria, MS-13 member Brenda Paz, 18, was found on the banks of the Shenandoah River last July, and federal officials have said they suspect that other MS-13 members were involved.

"We don't have the levels of violent crime that you all have in Northern Virginia at this point,'' Carter said. "We don't want it to get to that point.''

The news conference took place at a time of increasing concern over gang activity locally. A 16-year-old youth was assaulted with a machete May 10 on Edsall Road in the Alexandria area of Fairfax. All four fingers on his left hand were cut off, and his right hand was nearly severed. Hayner R. Flores, 18, has been charged.

Police called the machete attack part of a feud between MS -- widely seen as Northern Virginia's most violent and fastest-growing gang -- and the victim's gang, South Side Locos, or SSL.

In what police said was an unrelated gang incident Sunday night, Sandoval was shot and killed and a 16-year-old girl was wounded by an assailant on a bicycle who fired numerous rounds at them while they walked on a quiet street near the Washington & Old Dominion trail. Law enforcement sources have said the assailant had an "MS" gang tattoo on his forehead, short for MS-13.

Gang experts said the higher an MS tattoo is placed on the body, the more violent the crimes the person has committed. No arrests have been made, and the girl, who was shot in the back, is in stable condition.

A parade of federal officials, from agencies such as the Drug Enforcement Administration and the U.S. Marshals Service, vowed yesterday to stop gang activity through tough law enforcement and increased education for parents and students.

"This is beyond a regional problem. It is, in fact, a national problem," said Michael A. Mason, assistant director in charge of the FBI's Washington field office. He said the FBI is examining the structure of gangs such as MS-13 trying to see whether gang leaders can be targeted using laws such as those against running a criminal enterprise.

Federal officials used a similar approach to bring down Mafia crime leaders, and the Justice Department in recent years has become increasingly involved in the fight against gangs.

The $350,000 in funding announced yesterday will go to a Herndon-based gang task force started by Wolf in 2003 and headed by Summers. It is one of at least two gang task forces operating in Northern Virginia; the other, started by Virginia Attorney General Jerry W. Kilgore (R), is statewide.

Herndon Police Chief Toussaint E. Summers Jr., right, speaks at last night's town meeting. He said police patrols would be increased at Herndon High School.

At the meeting, which drew more than 300, residents received handouts of sketches of suspects and lists of police personnel working on gang violence.