WASHINGTON — US officials Wednesday unveiled the FBI's largest ever police corruption sweep saying 133 police, prison guards and army officers have been charged in a huge anti-graft crackdown in Puerto Rico.

The suspects face charges relating to possessing and distributing cocaine, and using firearms during a drug trafficking offense, the US Department of Justice said in a statement.

The arrests "are the result of Operation Guard Shack, the largest police corruption investigation in the history of the FBI," the statement read.

"Close to 750 FBI agents were flown in to Puerto Rico from across the country to assist in the arrests" early Wednesday.

A total of 129 people, including 60 Puerto Rican police officers, 16 municipal police, 12 prison officials, three Puerto Rico National Guard soldiers, and two US army officers, have been arrested.

Four others remain at large.

The indictments result from 125 undercover drug stings conducted by FBI agents in Puerto Rico between July 2008 and September 2010.

The defendants' participation "consisted of providing armed protection to a drug dealer during the sale of multi-kilogram quantities of cocaine."

If convicted the defendants face sentences "ranging from 10 years, up to life in prison," the DOJ statement read.

"The Justice Department?s commitment to rooting out and eradicating alleged corruption in our law enforcement ranks has never been stronger," said US Attorney General Eric Holder.

Puerto Rico is a Spanish-speaking Caribbean archipelago and US territory, which lies east of the Dominican Republic.