Several weeks before a vicious machete attack in the Lynbrook neighborhood, a resident filed a complaint about crowding and suspicious activity at a house there.

With gang crime and illegal boardinghouses a growing controversy in Springfield, a team of Fairfax County zoning, housing and health regulators paid a visit to check it out.

The inspectors found "no violations, only a nice family," according to the Fairfax supervisor for the area, T. Dana Kauffman (D-Lee).

But now, in the wake of the machete attack involving a group of youths outside the house, some residents and officials are questioning whether vigilance has been adequate to protect residents from the threat of gangs.

A 17-year-old, who a witness said was living at the house, has been arrested in the May 29 attack, and authorities issued a search warrant for the residence.

"This [attack] is disturbing on a number of levels," Kauffman said at a Board of Supervisors meeting yesterday. "How did we miss signs of trouble at this address?"

Moreover, he suggested that the problem of crowding is related to the problem of gangs and called for inspectors to be trained to "recognize red flags that point to potential gang concerns."

"Could these properties be hiding gang members and gang activities under our very noses?" Kauffman asked.

In much of Fairfax County and Northern Virginia, suburban neighborhoods are grappling with a rise in complaints about homes crowded with immigrants, as well as gang activity -- particularly that of Mara Salvatrucha, or MS-13.

Police and zoning regulators have searched for the right measures to effectively root out trouble while respecting civil liberties. Just last week, for example, Virginia State Police backed off a plan to allow some officers to make immigration arrests after immigrant rights advocates voiced opposition.

The case of the house at 6807 Lynbrook Dr. underscores the passions such issues provoke as well as their legal murkiness.

The house is a pleasant-looking brick split-level in a neighborhood of carefully tended lawns in southeastern Fairfax County.

One resident of the neighborhood, who has not been identified, filed a detailed report about activity there March 31.

"Since occupying the house in early 2005, no fewer than 21 different vehicles have been seen around the property," the complaint said. "Almost every evening a white panel van arrives with several young males who seem to be staying at the house. The van stays the night and leaves early the next morning."

Another neighbor, Frank Payne, a military retiree who lives diagonally across the street, said yesterday he perceived nothing dangerous.

"As far as I'm concerned, there's absolutely no problem over there whatsoever," he said. "They're quiet people."

The inspectors who were sent to the house, which appears to be rented, also found little of concern.

"The property was found to be occupied by the Rodriguez family, consisting of a husband, wife, son and two daughters," the inspectors said. "There was no indication of a multiple dwelling or multiple occupancy. The owners did acknowledge that they recently have had family gatherings of large numbers of relatives."

The machete attack, according to police, occurred after the 17-year-old suspect, who had been playing basketball in the driveway of the house, flashed MS-13 hand signs at the victim. Later, police said, the suspect and about six others approached the victim with machetes and possibly bats and sticks, according to search warrant documents.

A woman who answered the door at the house yesterday declined to comment.

Asked what signs the inspectors might have missed or what could have been done legally to prevent the attack, Kauffman offered no specifics, but he called for tougher measures to deal with immigration and gang issues. He also supports state laws that would make brandishing a machete a violation, just as brandishing a firearm is.

"It's clear that our federal officials have chosen to largely ignore immigration issues, leaving us to deal with the fallout in our neighborhoods," Kauffman said. "I have to be able to say to the neighbors of this house that we are doing everything we can for the short-term and long-term safety."