Fewer than three dozen police officers patrol the streets of Manassas Park, a small city of strip malls, quaint neighborhoods and about 15,000 people nestled between the corridors of interstates 95 and 66. Despite its size, its location has made it a supply stop in the flow of illegal immigrants, weapons and drugs into and throughout the region.

That’s why, one night in November, a team of more than 40 — made up of officers from the city’s Police Department, the Bureau of Alcohol, Tobacco, Firearms and Explosives and five other agencies — raided a Manassas Park apartment above a pink-painted antique shop on Route 28. They visited three other places in Manassas Park the same night, serving 11 search warrants, collecting five firearms and 1.5 kilograms of cocaine and arresting nine.

The raids marked the end of a two-year investigation into cocaine and gun trafficking conducted by the Northern Virginia Violent Crimes Task Force, which helps police departments contain criminal operations they might not be able to fight alone — and that, officials say, could spread across the Washington area if left unchecked.

“This give us far beyond what a locality like Manassas Park can accomplish,” said Frank Jones, the city’s mayor. “It is, in my mind, one of the most effective means of law enforcement.”

Now two years old, the task force combines local agencies’ intelligence resources with federal tactics, equipment and the ability to cross jurisdictional boundaries. Officials say it has targeted violent and repeat offenders, drug-trafficking hot spots, groups active in robberies and home invasions and murder-for-hire plots.

The force has led investigations that have resulted in more than 200 state and federal convictions, officials said.

The group, made up of 26 ATF agents, detectives and officers from the Fairfax County police and Sheriff’s Office, Alexandria police, Arlington County police, the Prince William County and Stafford County sheriff’s offices, Virginia State Police and Manassas Park police, operates out of ATF offices in Falls Church. Other agencies have been invited to join but might not be able to devote full-time personnel, officials said. The task force still operates in those areas when called upon.

Where these agencies might previously have worked together on individual cases, they now try to attack dangerous groups before they become larger problems.

“This task force is designed to go after the worst of the worst,” said Ashan M. Benedict, ATF resident agent in charge, who has led the force since its inception.

It has tracked illegal guns from straw purchasers in West Virginia, North Carolina and Florida, and drugs such as ecstasy and methamphetamines as they make their way here from Canada and Mexico. Once in Virginia, officials say, contraband often continues moving.

“There is so much Mexican dope here. It goes from here, right into the District,” said Richard Marinos, ATF assistant special agent in charge, as he stood outside the antique store after the raid.

In two cases, the task force’s undercover officers infiltrated home invasion and robbery crews from Pennsylvania and California.

Several Philadelphia area men were convicted this year for conspiring to rob a Fairfax County house known as a drug repository in October 2010. They arrived with guns, latex gloves and restraints — and five were soon arrested by members of the task force and, ultimately, sentenced to as much as 30 years in prison.

“When you wipe out a crew in these areas of Northern Virginia, that can have a lasting impact for several years,” Benedict said.

Lt. David Smith, of Fairfax County’s Criminal Intelligence Unit, supervises a location where undercover detectives connect with those crews. Although some gang activity has moved to areas with a lower cost of living, Smith said, Virginia counties remain rich targets for robbers, thieves and drug dealers.

“Northern Virginia is a wealthy area,” Smith said. “Criminals are attracted to the money and people come here to commit crimes.”

In interviews, two Northern Virginia members of Congress called the task force — which is staffed and mostly funded by the ATF and local agencies — a “national model” for local and federal cooperation. Both are given regular briefings on the task force’s work in their districts.

“Had they not been out there doing what they do, violent gangs would be roaming the streets of Northern Virginia,” said Rep. Frank R. Wolf (R) , who chairs a subcommittee for justice agency appropriations. “These are bad people; we would have had a serious problem.”

“In Fairfax County and Northern Virginia you have a climate of relatively low violent crime. We want to keep it that way,” said Rep. Gerald E. Connolly (D). “We understand that requires consistent investment in prevention and law enforcement.”

In Manassas Park, the task force has been invaluable as authorities fight drugs, robberies and other violence, says Jones, the mayor. His police force has only 32 sworn officers, so the additional resources and upgrade in investigative capability is “beyond a multiplier.”

“The existence of the task force is not debatable,” Jones said. “It has to continue.”