Three notorious outlaw motorcycle gangs have caught the attention of Bakersfield police who intend to do everything they can to hold any criminal activity in check, officers said Friday.

"They definitely have our attention," Bakersfield police homicide Sgt. Joe Aldana said of the Mongols, Vagos and Hell's Angels. "We are trained very well in gang enforcement. Criminal actions will not be tolerated and we will be very proactive."

He and gang officer Eric Littlefield urged the public to keep a hands-off approach to any sightings of gang members, but to be "good witnesses" if something does happen.

Their comments follow a May 30 stabbing death in Oildale that sheriff's reports indicate could be a rivalry between the Vagos and the Hell's Angels. Because of that incident and a warning from the sheriff's department, organizers of the annual Bakersfield Thunder Run canceled the June 12 event that was scheduled to begin at the Kern County Fairgrounds.

Aldana and Littlefield revealed for the first time Friday that last year's Thunder Run was marred by "a tense standoff" between about 20 members each of Hell's Angels and Vagos.

Deputies were present during the standoff and Bakersfield police officers, who had just left the event, returned, Aldana said. The police presence quelled any criminal activity and no arrests were made, he said.

Also, no arrests have been made in the May 30 stabbing death of 18-year-old Roger Anthony Violano and the wounding of Nerl Rinehart in front of the Pirate Tattoo Shop in the 1900 block of North Chester Avenue.

But a sheriff's search warrant says a witness reported a fight between two motorcycle groups, with seven wearing green and brown vests -- colors associated with Vagos -- and eight wearing black vests, which could be associated with the Hell's Angels. The stabbing victims were identified as Vagos members, the search warrant says.

About 90 minutes after the stabbing, deputies checked the registration of five motorcycles in front of the tattoo shop and three showed as Hell's Angels members, according to a sheriff's gang officer.

Littlefield said some Hell's Angels and Vagos live in Kern, but neither have a chapter here. He declined to say how many members live in Kern.

He said the Mongols have a chapter in Kern and members of that group have been here since the 1970s. But he said there have been no gang-related convictions for any of those motorcycle groups in Kern.

By contrast, other street gangs such as the Crips, Bloods and Hispanic gangs have numerous gang-related convictions.

Most people don't even know the Mongols are here, Littlefield said.

Police are also concerned that some support clubs have been seen in Kern -- clubs that aren't the gang themselves, but associate themselves with the gang. One wears 81, meaning the eighth and first letter of the alphabet, HA of Hell's Angels, Littlefield said.

While motorcycle gang members in Kern may have individually committed crimes, the investigations haven't been able to establish those crimes fall within the elements of gang activity, he said.

Also, the Mongols have been under -- until recently -- a court order not to display the Mongol logo and insignia since late 2008. That's when crackdown of the group resulted in 38 arrests in six states, including its leader, Ruben "Doc" Cavazos.

News reports about the history of the gangs say:

* The Mongols, a heavily Hispanic gang formed in 1969 in Montebello, has feuded with the Hell's Angels for denying membership to Hispanic men based on race.

* In 2002, members of the Mongols and the Hells Angels had a confrontation in Laughlin, Nev., at the Harrah's Laughlin Casino that left three bikers dead.

* The Hell's Angels date back to the 1940s and 1950s and now have chapters throughout the United States and several other countries. They have red lettering over a white background.

* The Vagos started in San Bernardino in the 1960s and have members across the western United States. They often wear green and brown.

Littlefield said it's important to note that motorcycle gangs are a small percentage of motorcycle riders.

"Just because someone wears a logo and rides a Harley doesn't mean he's a gang member," Littlefield said.