SAN DIEGO (Reuters) - Police and federal agents arrested more than 100 suspected gang members in San Diego and surrounding communities on Wednesday in a major operation on charges including drug trafficking and weapons violations, authorities said.

The arrests came as violent crime in San Diego has decreased slightly, and officials said the takedown struck a further blow against gangs in the area. San Diego saw violent crimes dip last year to 2,482 from 2,773 the year before, FBI statistics show.

Charges against those arrested included methamphetamine, cocaine and heroin trafficking, conspiracy, and federal firearms violations, according to court papers.

A total of 17 federal grand jury indictments and eight criminal complaints were filed in federal court against 119 people as part of the operation, the U.S. Attorneys' Office in San Diego said. About a dozen of the defendants were still at large, while the rest have been arrested, the FBI said.

If convicted, the defendants face prison sentences ranging from five years to life.

The arrests follow three investigations conducted over the course of more than a year that involved the use of wiretaps, U.S. Attorney Laura Duffy, who handles federal prosecutions in the San Diego area, told reporters.

Among those charged were two key Mexican Mafia members, court papers said. Street gangs were paying tariffs to the Mexican Mafia for being allowed to do gang business in the San Diego area, San Diego County Sheriff Bill Gore told reporters.

FBI Special Agent in Charge Keith Slotter said in a statement that the arrests mark one of the largest single takedowns ever to involve the San Diego office of the FBI.

"San Diego is inherently safer today because of the cooperation between our agencies working together to disrupt and dismantle the criminal activities of these dangerous individuals," Slotter said.

(Editing by Alex Dobuzinskis and Cynthia Johnston)