ATLANTA — Agents dealt a substantial blow to an extremely violent Mexican drug cartel with 175 arrests in the U.S. and Italy, Attorney General Michael Mukasey said Wednesday.

The Gulf cartel is responsible for importing tons of cocaine, methamphetamine, heroin and marijuana from Central and South America into the U.S. and then distributing it, Mukasey said.

The cartel is also believed to have laundered millions of dollars and has become a driving force behind escalating violence in Mexico and along the southwestern border of the U.S.

The arrests Tuesday and Wednesday were the result of a coordinated effort among hundreds of law enforcement officials. They were announced in Atlanta, identified as a regional hub for the cartel, where 43 people were arrested.

The Mexico-based cartel has high-level members in other regional hubs, such as Dallas, and is branching out into smaller cities such as Jackson, Miss., and Birmingham, Ala., said Drug Enforcement Administration agent William Matthews.

People were arrested in a dozen states as agents targeted the cartel's infrastructure, including transportation routes and distribution cells.

Through collaboration with Italian authorities, 10 people were also arrested in the Calabria region of Italy on charges related to drugs trafficked through New York.

"We're going after the top leadership on down to regional leaders," Matthews said. "By doing this we're trying to break their spine."

The arrests announced Wednesday were part of a 15-month investigation that has resulted in 507 arrests and the seizure of about $60.1 million, 16,711 kilograms of cocaine, 1,039 pounds of methamphetamine, 19 pounds of heroin, 51,258 pounds of marijuana, 176 vehicles and 167 weapons.

Officials said indictments were unsealed Wednesday morning in U.S. District Court in Washington, D.C., for three alleged leaders of the cartel: Ezequiel Cardenas-Guillen, Heriberto Lazcano-Lazcano and Jorge Eduardo Costilla-Sanchez. All three are believed to be in Mexico and are considered priority targets by American authorities, who are working with their Mexican counterparts to catch them.