A man already serving a 97-year sentence in California for sex trafficking has been charged in federal court in Delaware with conspiring to force three minors and a woman into commercial sex, and prosecutors allege he carried out part of the scheme on contraband cellphones from prison, the Justice Department announced Friday.

The indictment, unsealed Friday in the District of Delaware, names Jamar Geeter, 39, of San Francisco; Kalvin Carter Jr., 44, of Waldorf, Maryland; and Jada Hasty, 29, of Coatesville, Pennsylvania. All three are charged with conspiracy to commit sex trafficking of a minor by force, fraud and coercion, and with sex trafficking by force, fraud or coercion. Geeter and Hasty also face counts of sex trafficking of a minor, coercion and enticement of a minor, and producing child sexual abuse material. Geeter faces additional counts of producing and receiving such material. An indictment is only an allegation, and all three are presumed innocent unless proven guilty.

According to the department, the defendants conspired to compel three minors and one adult to engage in commercial sex acts in Delaware and elsewhere, using force, threats of force, fraud or coercion. Prosecutors allege that Geeter and Hasty recruited, harbored and transported two of the minors knowing, or in reckless disregard of the fact, that they were under 18. The pair also used cellphones and the internet to entice three minors into prostitution and produced sexual abuse images of two of the children, the department said.

According to court documents cited by the department, Geeter is serving his California sentence on unrelated state sex trafficking convictions, and prosecutors allege he used contraband cellphones while incarcerated for some of the conduct in the new case. Jimmy Paul, the special agent in charge of the FBI's Baltimore field office, put it more bluntly. Citing court documents, he said Geeter, "already a convicted sex trafficker, continued directing abuse from behind bars with Jada Hasty and Kalvin Carter Jr. as his willing accomplices." Paul said the investigation stretched from coast to coast and rescued three children and one woman.

Geeter's earlier case came out of San Francisco. In March 2016 he was found guilty of 16 felony counts, including human trafficking, rape, and pimping and pandering, after a two-month trial in a case involving two girls who were 14 and 16 when the crimes occurred in 2014, CBS San Francisco reported at the time. In April of that year, Superior Court Judge Jerome Benson sentenced him to 97 years to life in state prison, according to SFGATE, which reported that it was the city's first case brought under Proposition 35, the state measure that set tougher sentencing rules for trafficking convictions.

Federal court records list the Delaware case, United States v. Geeter, as filed on Feb. 17. Docket entries dated Friday include the indictment and an order detaining a defendant pending trial.

If convicted, each defendant faces a minimum of 15 years and as much as life in prison on the force, fraud and coercion trafficking charges. Geeter and Hasty face the same range on the counts involving minors, and the child sexual abuse material charges carry 25 to 50 years for Geeter and 15 to 30 years for Hasty.

Assistant Attorney General A. Tysen Duva, who heads the Criminal Division, said the three "are alleged to have exploited and abused four victims," three of them children, "for their financial gain." Benjamin L. Wallace, the U.S. attorney for Delaware, said trafficking schemes "don't stop at state lines" and that his office would "pursue anyone charged with exploiting minors in Delaware, no matter where the perpetrators reside."

The FBI's Delaware Violent Crime and Safe Streets Task Force and the Delaware State Police are investigating. Trial Attorney Nicole Raspa of the Criminal Division's Human Rights and Special Prosecutions Section and Assistant U.S. Attorney Claudia Pare are prosecuting. The department's announcement did not include a response from any of the defendants or their lawyers.