CONCORD, N.H. — Three Boston men were sentenced to several years in prison for bringing a 15-year-old Massachusetts girl to a New Hampshire motel for sex with paying clients, authorities said Thursday.

The US Attorney for New Hampshire said Andy Pena, 21, and Hansel German, 25, were sentenced to eight years in prison for aiding and abetting human trafficking for the purposes of prostitution. Enoc Ayuso was sentenced to five years for his role in the conspiracy.

A fourth defendant, Rafael Reyes, whose hometown was not identified, pleaded guilty to the same charge as German and Pena and will be sentenced next week.

Clients were solicited through the online classified advertising site Backpage.com, authorities said.

Assistant US Attorney Nick Abramson said investigators were unable to identify the clients who paid to have sex with the minor at the LaQuinta Inn and Suites in Salem in 2014.

US Attorney Emily Gray Rice said the victim played a critical role in the four convictions.

‘‘She had been placed into a sinister and abusive world,’’ Rice said, praising the ‘‘bravery of a minor child who came forward courageously to tell her story.’’

Rice appealed to other victims of sex trafficking to come forward as well.

‘‘Let us help you out of that world and put the people profiting from it behind bars,’’ she said.

Rice said the Boston Police Department provided the initial leads on the men’s activities and movements and members of the New Hampshire division of Internet Crimes Against Children provided the forensic skills to detect electronic evidence.

The teamwork helped build an overwhelming case against the four suspects, she said.

Officials said the victim is still grappling with her ordeal.

‘‘It’s been a very long healing process for her,’’ said Jennifer Hunt, federal victim-witness advocate. ‘‘She felt very used, embarrassed and ashamed, but has come to a place where she realizes this was not her fault.’’