LAUGHLIN, Nev.?Rival motorcycle gangs armed with guns and knives clashed on a crowded casino floor early Saturday, leaving three dead and at least 12 wounded as terrified gamblers ducked for cover.

The shooting, the worst ever inside a Nevada casino, occurred during a weekend gathering of motorcycle groups, including the Mongols and Hells Angels.

Police said the violence erupted when a Mongol member walked into a group of Hells Angels. Sixty to 70 people, armed with guns and knives, were involved in the violence inside the entrance to Harrah’s casino, authorities said.

All three of the dead were bikers, police said. Only one person was arrested.

Authorities warned of the danger for further violence, as rumors of retaliation have resurfaced. To help safeguard against further violence, SWAT teams and law enforcement officers from across Arizona and Nevada were called in.