U.S. federal authorities have arrested dozens of members of several white supremacist prison gangs in Texas on charges of drug trafficking and kidnapping.

Authorities announced Monday that 57 people were charged in the conspiracies. Forty-two were arrested last week, nine were already in custody on unrelated charges, and six others are being sought.

The defendants are linked to several violent and racist prison gangs, including the Aryan Circle, the Aryan Brotherhood of Texas, the Peckerwoods, the Soldiers of Aryan Culture, and the Dirty White Boys, the 55-count indictment said.

“Not only do white supremacist gangs subscribe to a repugnant, hateful ideology, they also engage in significant, organized and violent criminal activity,” Attorney General Jeff Sessions said in a statement.

The drug operation operated from October 2015 through April 2018 and was occasionally violent. Four of the defendants kidnapped someone in an effort to obtain drug proceeds that they believed were owed to them. The victim was beaten and had part of a finger lopped off with a hatchet.

Agents also seized about $376,500 in cash and intercepted more than 190 kilograms of methamphetamine, along with 31 firearms, as part of their investigation, U.S. Attorney Erin Nealy Cox said Monday during a news conference.