Federal authorities have arrested someone in the case of a 17-year-old developmentally disabled Massachusetts girl found with a man in Rhode Island after her parents reported her missing.

    Rhode Island U.S. Attorney Peter Neronha said Thursday afternoon the person would be making an initial appearance Friday in Providence. No further details were released.   

    Medfield Police Chief Robert Meaney Jr. said earlier that Brittany Thompson was located ``safe and unharmed'' walking down a Coventry, R.I., street Thursday. Meaney didn't say if it was the same man she was seen leaving the Medfield library with on Monday afternoon.

    He had said the investigation was ongoing.

    Brittany's parents publicly appealed Wednesday for her return and said she may have met someone online. (Associated Press)