FARGO, N.D. (AP) – Top federal prosecutors from North and South Dakota have added human trafficking to their list of crimes affecting Native Americans at an increased rate in the two states.

U.S. attorneys Brendan Johnson of South Dakota and Timothy Purdon of North Dakota said during a conference on family violence Tuesday that both states are seeing more cases of girls and young women being recruited for prostitution and drug rings.

Three new indictments for human trafficking have been handed down in South Dakota in the last three months, Johnson said.

“You have people who treat their victims like they're not humans,” Johnson said after talking to a group that included police, social workers, prosecutors, counselors and community leaders.

The operations are formed mainly in populated areas, but American Indian girls are particularly at risk, the prosecutors said. Some of them were recruited by a Sioux Falls-area man who was convicted last year of sex trafficking of a child.

“These young girls were brutalized. They were humiliated,” Johnson said.

Brandon Thompson, 28, of Tea, S.D., was sentenced to life in prison on the sex trafficking charge.

“This is one area where the federal government has gotten it right,” Johnson said of the penalty.

A recent sex trafficking case in North Dakota involved several victims from the Fort Berthold Reservation. Dustin Morsette, 22, of New Town, was convicted of sex trafficking, sexual abuse, drug trafficking and witness tampering. He is awaiting sentencing.

Authorities said Morsette recruited minors and young adults to be part of a gang he described as the Black Disciples. He allegedly forced gang members to distribute marijuana for him and engage in sex acts with him.

One of the investigators in that case, Bureau of Indian Affairs agent Mike White, said the increase in oil workers has added to worries about sex trafficking. But he said recent convictions on human trafficking and other violent crime has made victims and others more willing to help law enforcement.

“I have hope. I've seen it already,” White said in an interview Tuesday. “Once they know people are being prosecuted, they are coming forward.”

Purdon, the U.S. attorney from North Dakota, said the campaign against violent crime on the reservation is a long process. He noted that an American Indian woman born in the United States has a 1-in-3 chance of being sexually assaulted in her lifetime.

“Improving public safety in Indian country is not something you are going to knock out in two years,” he said. “If we can sustain this for a period of years, I am hopeful, I am confident, we can impact some of these statistics we find to be unacceptable.”