Disputing a child welfare/social services investigation for neglect/abuse in NC?

A friend of mine and her husband had their two month old daughter taken away a month ago. An investigator came into their home at 8:50 pm and told them that they were sending the little girl to live with the husband's parents. They had recieved a call about suspected abuse. The child was taken to a doctor and essed- no physical, ual, or emotional injury or abuse evident nor neglect evident. They were both given drug tests- which were negative. Their home was not deemed unfit either- so how long can the DSS keep them away from their child? (They are allowed to visit her at his parents home as much as they like, but cannot take her away or spend the night...) What are the rights of parents being investigated in NC? I am aware that I may not have the whole story, as I am not the one being investigated. I do know, however, that there are cases where the Dept. of Social Services oversteps their boundaries or drags out an investigation on absolutely no legal basis or evidence. Anyone have any insight?