A South Dakota couple is accused of using their home as a base for an underage sex trafficking operation.

Twenty-six-year-old Brandon Thompson and his 30-year-old girlfriend, Megan Hayes, are accused in federal court of conspiring to sell the services of underage prostitutes through online ads.

U.S. Attorney Brendan Johnson would not comment on the extent of the couple's alleged criminal activities or on the number of underage people involved. Three are mentioned in the complaint.

The arrests of the couple late last week came after a six-month investigation sparked by a tip to local police. The investigation included the FBI, the South Dakota Division of Criminal Investigation, the federal Bureau of Alcohol, Tobacco and Firearms and the Minnehaha County Sheriff's Department.

Authorities say Thompson also has a criminal record or pending charges in Minnesota, Illinois and Wisconsin.