Is the baby cat DEAD??

Our cat had her babies under my next door neighbours house, it was under a gap so we couldnt do anything but just let the kittens and mum be. The mother however came occasionally for food. Today she carried one baby kitten in her mouth to ourt front doorstep and shes lying there now. The baby kitten is dead. Does the mother have anymore kittens under our neighbours house?Coz shes only with one right now.