NEW YORK — An ex-convict accused of bilking several college students out of nearly $1 million and forcing some into prostitution or unpaid labor was arrested Tuesday on extortion and sex trafficking charges.

Lawrence “Larry” Ray was previously known for his role in helping to send former New York City police commissioner Bernard Kerik, who was a close confidant of Rudy Giuliani, to prison.

Federal prosecutors said Ray, 60, used “physical, sexual and psychological abuse” to extort money from five different students at Sarah Lawrence College, a private liberal arts college outside New York City. He convinced them they were indebted to him, authorities said, subjecting them to “grueling interrogations” that spanned hours and deprived them of food and sleep.

Ray was taken into custody Tuesday and expected to appear hours later in Manhattan federal court. He had previously denied the allegations, saying they were the result of a conspiracy against him. It was not clear whether he had a defense attorney who could comment on the charges.

U.S. Attorney Geoffrey Berman told reporters the investigation was prompted by an article that appeared last year in New York magazine.