ALBANY — Paul DerOhannesian, a criminal defense attorney from Albany, has been retained by Keith Raniere, the co-founder and leader of NXIVM who is facing federal charges of sex trafficking and conspiracy to commit forced labor.

DerOhannesian, a former assistant district attorney in Albany, filed a notice in U.S. District Court in Brooklyn on Tuesday indicating he will represent Raniere in the case.

Raniere was arrested March 25 in Puerto Vallarta, Mexico, on a federal criminal complaint filed in February by the U.S. attorney's office for the Eastern District of New York. Raniere made his first court appearance March 27 in Fort Worth, Texas, and has been held at a federal prison in Oklahoma City for the past two weeks. He remains in the custody of U.S. marshals without bond and is being returned to Brooklyn in the coming days, according to people briefed on his case.

Raniere, 57, is the leader of an international "self-help" organization that has been headquartered in the Capital Region for roughly two decades and has been described by some experts as a cult.

The federal complaint alleges that Raniere took part in forming a secretive group within NXIVM in which women said they were coerced into joining a slave-master club. The women, some of whom said they were pressured to have sex with Raniere, told federal authorities that a female doctor associated with NXIVM used a cauterizing iron to brand them with a design on their lower abdomen that contained the initials of Raniere and Allison Mack, an actress and NXIVM associate who is listed in the complaint as an unnamed co-conspirator.

In court filings, U.S. Justice Department officials said that Raniere fled to Mexico last November when the federal investigation began. They have asked for him to be detained without bond while the case is pending, describing him as a flight risk and danger to the community.

The federal investigation has broadened beyond the slave-master club allegations. Two weeks ago, FBI agents searched the Saratoga County residence of NXIVM's president, Nancy Salzman.

Salzman is a registered nurse who has been listed as a co-founder of NXIVM.