A southeast Nebraska man has been sentenced to between 40 and 55 years in prison for sexual assault that authorities say occurred over three years beginning when the victim was 14.

The Lincoln Journal Star reports 28-year-old James W. Graves, of Salem, was sentenced Tuesday on two counts of first-degree sexual assault.

Graves, who pleaded guilty in August, also must register as a sexual offender for 25 years.

An investigation launched by the Nebraska State Patrol determined Graves had repeatedly sexually assaulted the victim over three years.