You will encounter an elven woman called Malena in The Witcher 2, whom some guards harass at Lobinden. The guards will call her an elven witch and accuse her of being a Scoia’tael Spy. The guards have ...
The presence of nekkers is certainly enough to suggest that Malena wasn't lying about the reasons behind the soldiers' failure to return, but you need to find the bodies to prove that definitively.