As many as 1 million gang members are believed responsible for as much as 80 percent of crime in America -- and the gangs are spreading across the country, according to a Justice Department gang threat assessment.
Approximately "1 million gang members belonging to more than 20,000 gangs were criminally active within all 50 states and the District of Columbia as of September 2008," the report says.
"Criminal gangs commit as much as 80 percent of the crime in many communities, according to law enforcement officials throughout the nation," the report notes as part of its key findings. "Typical gang-related crimes include alien smuggling, armed robbery, assault, auto theft, drug trafficking, extortion, fraud, home invasions, identity theft, murder and weapons trafficking."
A copy of the threat assessment, prepared by the Justice Department's National Gang Intelligence Center and the National Drug Intelligence Center, was obtained by ABC News from U.S. law enforcement officials on Friday.
Historically, gangs have been a bigger problem for cities, but that may be changing.
"Gang migration from urban communities to suburban and rural locations, which began more than two decades ago, is a significant and growing problem in most areas of the country," the report says. "Gangs are now fully entrenched in many communities across the nation."
In a speech before the International Association of Chief of Police in November 2008, FBI Director Robert Mueller described the problem gangs pose in Chicago.
"We are working closely with law enforcement in Chicago to combat gang violence," he said. "Chicago law enforcement estimates there are at least 60,000 gang members in the community -- far outnumbering police officers. There are hundreds of homicides each year, the majority of which are gang-related."
"The FBI has, in the past, investigated gangs as criminal enterprises," Mueller said. "Our traditional approach has been to target their leadership and dismantle them from the top down. But the increase in gang violence called for a non-traditional approach. It is not enough to just gather intelligence about the violent offenders. We have to interrupt that violence."
The report notes that smaller local gangs and crews are involved in the drug trade.
"Local street gangs, or neighborhood-based street gangs, remain a significant threat because they continue to account for the largest number of gangs nationwide," the report says. "Most engage in violence in conjunction with a variety of crimes, including retail-level drug distribution."
The report notes that prison gangs are becoming more involved with drug trafficking organizations, too.
"Prison gangs exert considerable control over midlevel and retail-level drug distribution in the Southwest region and in Southern California," the report says.
The FBI houses the National Gang Intelligence Center, which helped prepare the report, and which was established by the FBI; the Drug Enforcement Administration; the Bureau of Alcohol, Tobacco, Firearms and Explosives; and the U.S. Marshals. Last October, elements from the Department of Homeland Security joined the center for the first time.