FONTANA, Calif. — Authorities have arrested dozens of people and seized guns, drugs and ammunition in a crackdown on two gangs operating in San Bernardino County.

Fontana police on Thursday announced the results of a six-month investigation that involved more than 350 local and state law enforcement officers.

The crackdown was aimed at the South Fontana street gang and Mexican Mafia prison gang.

Authorities say they arrested 67 people — including 35 on Thursday — on allegations ranging from cocaine, heroin and meth trafficking to attempted murder.

Nineteen handguns, shotguns and assault-style rifles were seized.