ST. PAUL, (AP) - The last of four family members charged in a sex trafficking operation that spanned nearly two years in Minnesota has been sentenced to 40 years in prison.

The Ramsey County Attorney's Office says Otis Washington's sentence is the longest one imposed for a sex trafficking defendant in state history.

The 30-year-old convict, his brother and two of their uncles were charged in the sex trafficking operation that involved numerous victims and multiple communities in Minnesota from September 2010 to July 2012.

According to the criminal complaints, authorities began investigating after a woman emailed police, saying her 15-year-old granddaughter was taken to a home where women were being sold for sex. Prosecutors say the brothers used eight email addresses and 30 phone numbers to place hundreds of ads on adult-oriented websites.