At least 61 members of the Southern California-based Mongol Motorcycle Club were arrested under a federal racketeering indictment that included charges of murder, attempted murder, assault, as well as gun and drug violations, said Mike Hoffman, spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives.
Federal and local agents had a total of 110 federal arrest warrants and 160 search warrants that were being served across Southern California and in Nevada, Oregon, Colorado, Washington and Ohio.
The sweep, dubbed Operation Black Rain, was to continue throughout the day Tuesday, agents said.
During some arrests, sharpshooters stood guard on surrounding rooftops and motorcycles were lined up and confiscated.
"It's going to be a large hit to their organization, we are arresting many of their top members," Hoffman said.
The bust was the biggest takedown of a motorcycle gang, said U.S. Attorney Thomas O'Brien.
His office was set to ask a judge for an injunction that would seize the Mongols' trademarked name, a first for federal authorities. If the order is approved, any Mongol would no longer be able to wear a jacket or ride a bike with the gang's name.
"It would allow law enforcement to seize the leather jackets right off their back," O'Brien said.
Among those arrested were the gang's former national president Ruben Cavazos.
Hoffman said the Mongols had been recruiting members of Los Angeles street gangs to assist in their operations. The Mongols are primarily Latino and formed because the Hells Angels refused to allow Hispanic members.
Four ATF agents infiltrated the gang and were accepted as full members, a difficult process that requires winning the trust of the gang's top leaders over a period of months, Hoffman said.
The agents were required to live away from their families in homes set up to make it look like they lived a Mongols lifestyle, Hoffman said. Four undercover women ATF agents also were involved in the operation, pretending to be biker girlfriends and attending parties with the agents. Women are not allowed to become full members of the gang.
"If you go to a party all the time and you don't ever bring a girl around, it's kind of weird," Hoffman said. "Someone might get suspicious."
To be accepted in the gang, the ATF agents had to run errands and were subject to a background check by private detectives.
The undercover agents observed a changing dynamic within the Mongols. As the gang recruited more Los Angeles street gang members - many of whom didn't have motorcycles and came from Latino gangs The Avenues and 18th Street - tensions grew.
The new members remained loyal to the powerful Mexican Mafia gang, which operates within the state's prison system, Hoffman said.
"That caused kind of a friction between the other guys with bikes," Hoffman said. "It's supposed to be a motorcycle club and they were just gangster thugs involved in the narcotics trafficking."
Cavazos authored a memoir of his life called "Honor Few, Fear None: The Life and Times of a Mongol," published by HarperCollins in June.
HarperCollins publicist Sarah Burningham in New York City said she only handles book-related issues for Cavazos, but would forward an e-mail from The Associated Press requesting comment.
Another former Mongols national president, Roger Pinney, alleged in an interview with The Associated Press that Cavazos was the problem, not the club in general.
"They were just on the verge of cleaning up their act," said Pinney, who is no longer a member and is serving probation from his role in an infamous brawl in Laughlin, Nevada, in 2002. "It's not a club-run deal, it's individuals who are the ones who decide to commit crimes."
Pinney said he warned other club members that Cavazos was trouble, but said he doesn't believe the raid will force the Mongols off the road.
"This is all going to blow over. The Mongols aren't going away, and neither are the Hells Angels," he said.
Five Mongols members were sentenced this year to Nevada state prison and two got probation for their roles in a deadly casino brawl with rival Hells Angels during a 2002 motorcycle rally in the Colorado River resort town of Laughlin. Three people died in the fight.