(MADISON, Wis.) — Authorities on Monday called for 2,000 volunteers to help in a ground search for clues in the disappearance of a Wisconsin girl whose parents were gunned down in their home last week.After an initial ground search on Thursday in which 100 volunteers helped search for clues into 13-year-old Jayme Closs’ disappearance, Barron County Sheriff Chris Fitzgerald said such searches wouldn’t resume unless investigators received a tip that justified them continuing.Fitzgerald told The Associated Press on Monday that “something triggered” the decision to conduct another ground search that starts Tuesday, but he declined to elaborate.